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302 Cards in this Set
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What is a mineral?
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A natural, inorganic substance with a characteristic chemical composition. Ususually may have a characteristic crystal structure.
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GI1: Introduction
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Chemical Composition
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Kinds and relative quantities of atoms that make up a material.
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GI1: Introduction
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Crystal Structure
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Regular, repeating internal arrangement of atoms in a material.
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GI1: Introduction
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Trace Elements
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Atoms that are not a part of a gem's essential chemistry. May also effect the color of a stone, therefore Variety.
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GI1: Introduction
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Amorphous
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A material with no internal crystal structure or recognizable external shape. Includes: Amber, natural and manmade glass, and plastic.
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GI1: Introduction
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Organic
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Produced by, or derived from, a living organism.
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GI1: Introduction
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Gem Species
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A broad gem category based on chemical composition and crystal structure. Ex: Corundum, Pyrope, Almandine, and Spessartine
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GI1: Introduction
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Gem Variety
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A subcategory of species, based on color, transparency, or phenomenon. Ex: Ruby and Sapphire of Corundum. Or Aquamarine and Emerald of Beryl
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GI1: Introduction
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Phenomenon
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Unusual optical effect displayed by a gem. Ex: Play of Color (Opal), Asterism (Star Sapphire), Chatoyancy (Chrysoberyl)
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GI1: Introduction
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Gem Group
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A family of gems made up of several closely related mineral species. Ex: Feldspar and Garnet
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GI1: Introduction
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Isomorphous Replacement
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Substitution of one chemical element for another in the crystal structure of a mineral, while basic crystal framework is maintained. Ex: Pyrope and Almandine, or a combination of both within a Garnet.
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GI1: Introduction
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Synthetic Gem
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A laboratory creation with essentially the same chemical composition, crystal structure, and properties as its natural counterpart.
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GI1: Introduction
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Imitation Gem (Simulant)
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Any material that can resemble a desired gem of higher value, and is often used in its place. The material can be natural or manmade.
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GI1: Introduction
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Transparent
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Description of a material that's capable of transmitting light so objects viewed through it appear clear and sharp.
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GI2: General Observation
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Translucent
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Description of a material that's capable of partially transmitting light so an image seen through it appears obscure, with a vague outline.
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GI2: General Observation
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Opaque
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Description of a material that's unable to transmit light, so an image can't be seen through it.
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GI2: General Observation
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Luster
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The appearance of a material's surface in reflected light. High to Low: Metallic - Adamantine - Subadamantine - Vitreous - Subvitreous - Greasy - Resinous - Waxy - Dull.
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GI2: General Observation
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Cleavage
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A smooth, flat break in a gemstone parallel to the planes of atomic weakness. Ex: Topaz, Feldspar, Diopside, and Spodumene.
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GI2: General Observation
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Parting
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A flat break in a gemstone parallel to a twinning plane. Ex: Corundum
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GI2: General Observation
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Fracture
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Any break in a gem other than cleavage or parting.
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GI2: General Observation
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Conchoidal Fracture
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A curved and ridged fracture in a gemstone, extending from the surface inward.
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GI2: General Observation
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Splintery Fracture
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A gemstone fracture that looks like broken wood, resulting from the fibrous structure of certain gems.
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GI2: General Observation
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Granular Fracture
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A sugary or grainy fracture that appears in microcrystalline aggregates.
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GI2: General Observation
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Fire
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The flashes of spectral color you see in a polished gem, especially a diamond.
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GI2: General Observation
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Dispersion
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The separaton of white light into spectral colors.
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GI2: General Observation
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Optic Axis
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The SR direction in a DR stone.
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Class
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Refraction
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The change in speed and possible bending of light as it passes from one material to another. The speed of Refraction depends on Optical Density and The Angle of Incidence.
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GI3: Refraction and The Refractometer
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Angle of Incidence
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The angle at which a ray of light strikes a surface, measured from the Normal.
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GI3: Refraction and The Refractometer
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Normal (Refraction)
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An imaginary line perpendicular to the point where a ray of light strikes the surface.
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GI3: Refraction and The Refractometer
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Oblique Angle
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Any angle other than a right angle.
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GI3: Refraction and The Refractometer
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Angle of Refraction
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The angle between the Normal and a reflected light ray's new path.
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GI3: Refraction and The Refractometer
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Critical Angle
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Angle between the Normal and the maximum angle of refraction.
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GI3: Refraction and The Refractometer
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Refractive Index (RI)
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A measure of the change in the speed and the angle of light as it passes from one material to another.
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GI3: Refraction and The Refractometer
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Refractometer
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An instrument that measures the Critical Angle of a gem and translates it directly into RI.
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GI3: Refraction and The Refractometer
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Polarization
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Limiting a light beam to one vibration plane that's perpendicular to its direction of travel. Whether a gem polarizes light depends on its internal symmetry.
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GI3: Refraction and The Refractometer
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Singly Refractive (Isotropic)
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Possessing the same physical or optical properties in all crystal directions. Cubic and Amorphous materials are SR.
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GI3: Refraction and The Refractometer
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Doubly Refractive (Anisotropic)
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Possessing different physical or optical properties in different crystal directions. Most colored stones are DR.
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GI3: Refraction and The Refractometer
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Birefringence
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The numerical difference between DR gem's highest and lowest RIs.
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GI3: Refraction and The Refractometer
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Optic Character
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The number of optic axes in a doubly refractive stone.
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GI3: Refraction and The Refractometer
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Uniaxial
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Doubly refractive with one optic axis.
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GI3: Refraction and The Refractometer
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Biaxial
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Doubly refractive with two optic axes.
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GI3: Refraction and The Refractometer
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Hemicylinder
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Half cylinder in a refractometer, made of high-lead, high-RI glass, on which the stone is placed.
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GI3: Refraction and The Refractometer
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Monochromatic Light
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Light that consists of only one wavelength and one hue.
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GI3: Refraction and The Refractometer
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Contact Liquid
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Liquid that makes an optical contact between a refractometer's hemicylinder and the material bring tested.
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GI3: Refraction and The Refractometer
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Over The Limit (OTL)
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Description of a gem with an RI higher than that of the contact liquid. Usually above the scale of 1.80.
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GI3: Refraction and The Refractometer
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Spot Reading
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Method used to determine RI on a gem's curved surface.
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GI3: Refraction and The Refractometer
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Birefringence Blink
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A method of determining birefringence that involves looking for a light-to-dark or green-to-red change in spot.
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GI3: Refraction and The Refractometer
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Optic Sign
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Statement of the relationship between a DR stone's two RIs.
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GI3: Refraction and The Refractometer
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Ordinary Ray
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The polarized ray that transmits through a uniaxial stone with an RI that remains constant.
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GI3: Refraction and The Refractometer
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Extraordinary Ray
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The polarized ray that transmits through a uniaxial stone with a varying RI.
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GI3: Refraction and The Refractometer
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What is the most accurate refractometer spot-reading method?
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50/50 method
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GI3: Refraction and The Refractometer
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To check a spot reading for Birefringence Blink, you must:
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Remove the magnifier and use white light and the polarizing filter.
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GI3: Refraction and The Refractometer
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The highest possible RI obtainable on the refractometer is determined by the:
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Contact Liquid
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GI3: Refraction and The Refractometer
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Polariscope
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An instrument that helps you study the interaction of transparent-to-translucent gems with polarized light.
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GI4: Polariscope Testing
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Polarizing Filter (Polariscope)
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A plastic disk embedded with specifically oriented, microscopic crystals, designed to transmit polarized light. Oriented on the top and bottom of the Polariscope.
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GI4: Polariscope Testing
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Polarizer (Polariscope)
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The Polariscope's lower polarizing filter, which remains stationary.
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GI4: Polariscope Testing
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Analyzer (Polariscope)
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The Polariscope's upper polarizing filter, which can rotate.
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GI4: Polariscope Testing
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Uncrossed Filters (Polariscope)
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The Polariscope's open, or "light", position, with the light-transmitting directions of the analyzer and polarizer to each other.
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GI4: Polariscope Testing
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Crossed Filters (Polariscope)
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The Polariscope's closed, or "dark", position, with the light-transmitting directions of the analyzer and polarizer perpendicular to each other.
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GI4: Polariscope Testing
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Anomalous Double Refraction (ADR)
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A false indication of double refraction in a material, caused by internal strain that occurs during formation. Look for snake-like bands during testing.
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GI4: Polariscope Testing
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Crosshatch Effect
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A pattern of intersecting, shadowy lines that resemble woven fabric.
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GI4: Polariscope Testing
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Optic Figure (Polariscope)
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A characteristic light pattern that helps identify a gem's optic character.
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GI4: Polariscope Testing
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Isochromes
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The concentric rings of an optic figure.
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GI4: Polariscope Testing
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Brush
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A shadowy line across an optic figure that's wide at the ends and narrow in the center.
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GI4: Polariscope Testing
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Isogyres
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The dark intersecting brushes of an optic figure.
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GI4: Polariscope Testing
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Bull's Eye
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A uniaxial optic figure with a central open area that resembles the center of a target.
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GI4: Polariscope Testing
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Airy's Spiral
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A uniaxial optic figure that resembles a pinwheel or a cross with curving arms, surrounded by rings.
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GI4: Polariscope Testing
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Double-Brush Biaxial Optic Figure
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A figure that resembles a uniaxial optic figure because the angle between the optic axes is so small the brushes seem to intersect.
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GI4: Polariscope Testing
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Interference Colors
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The iridescent colors that result from the interaction of light ray's traveling along the same path.
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GI4: Polariscope Testing
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What cannot be tested (reliably) in a Polariscope?
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An Opaque tablet, assembled stones, a red stone, or an OTL stone.
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GI4: Polariscope Testing
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If a gem gets noticeably darker during the Polariscope confirmation test, it is:
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DR
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GI4: Polariscope Testing
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You should check for Optic Character if:
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A DR stone might be confused with one that has a different optic character.
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GI4: Polariscope Testing
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When you test a round brilliant gem with a high RI in the Polariscope, you should:
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Turn the gem on its side.
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GI4: Polariscope Testing
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When you test a small stone in the Polariscope, it can be helpful to:
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Place a Refractometer's magnifier on the analyzer.
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GI4: Polariscope Testing
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What are the two value categories of Synthetic Production Processes?
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Low cost, High Volume and High Cost, Low Volume.
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CS5: Synthetics and Imitations
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What are the two main types of Synthetic Gem Processes that modern Synthetics are derived from?
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Melt and Solution processes.
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CS5: Synthetics and Imitations
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Melt Process
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A Synthetic-Crystal growth method in which the chemical mixture is melted, then recrystalized. Common melt processes are: Flame Fusion, Pulling, Floating Zone Process, and Skull Melt.
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CS5: Synthetics and Imitations
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Solution Process
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A growth method in which the Synthetic Crystal grows from a dissolved chemical mixture, sometimes at high temperature and pressure. Common Solution processes are: Flux Growth, Hydrothermal Growth, and Spontaneous Nucleation.
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CS5: Synthetics and Imitations
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Flame Fusion
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A process in which powdered chemicals are dropped through a high-temperature flame onto a rotating pedestal to produce a synthetic crystal. The result is a cylindrical synthetic crystal called a Boule.
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CS5: Synthetics and Imitations
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Pulling
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A process in which the synthetic crystal grows from a seed that is dipped into a chemical melt, then pulled away as it gathers material.
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CS5: Synthetics and Imitations
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Seed Crystal
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A tiny crystal used as a template to control the size, speed, or direction of growth and the shape of a growing synthetic crystal.
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CS5: Synthetics and Imitations
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Floating Zone
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A melt process where a heating unit passes over a rotating solid rod of chemicals until it forms a synthetic crystal.
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CS5: Synthetics and Imitations
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Skull Melt
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A Synthetic-Crystal growth method that uses cooling pipes around an interior of melted chemical ingredients. Used to synthesize CZ crystals.
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CS5: Synthetics and Imitations
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Flux Growth
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A process in which nutrients dissolve in heated chemicals, then cool to form synthetic crystals.
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CS5: Synthetics and Imitations
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Hydrothermal Growth
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A process in which nutrients dissolve in a water solution at high temperature and pressure, then cool to form synthetic crystals. The only method for growing quality synthetic quartz.
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CS5: Synthetics and Imitations
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Other Synthetic Processes
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°Synthetic Opal's Three Step Process
°Ceramic Processes: Finely ground powder is heated, sometimes under pressure, to produce a fine-grained solid material. |
CS5: Synthetics and Imitations
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Assembled Stone
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Two or more separate pieces of material joined to form a unit. Includes doublets and triplets.
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CS5: Synthetics and Imitations
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Disclosure
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Clearly and accurately informing customers about the nature of the goods they buy.
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CS5: Synthetics and Imitations
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Low Cost and High Volume characterize which process?
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Flame Fusion
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Which synthetic process developed rapidly due to laser research in the 1960s?
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Pulling Method (Melt Synthetic Process)
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CS5: Synthetics and Imitations
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Crucibles that work best for Flux Growth are made of:
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Platinum
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CS5: Synthetics and Imitations
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Which synthetic process uses an autoclave?
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Hydrothermal Growth
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CS5: Synthetics and Imitations
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Synthetic Opal is grown using microscopic silica spheres that are produced by:
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Precipitation
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CS5: Synthetics and Imitations
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A "snakeskin" structural pattern is typical of:
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Synthetic Opal
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CS5: Synthetics and Imitations
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The flux used in Flux Process is a solid material that, when molten:
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Dissolves other materials
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CS5: Synthetics and Imitations
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The Hydrothermal Synthetic Process requires a:
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Pressurized steel container and crushed chemical ingredients
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CS5: Synthetics and Imitations
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What kinds of stones are usually fashioned into a "Scissor-Cut"?
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Flame-Fusion Synthetic Spinel and Synthetic Corundum. Not conclusive.
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GI10: Separation and Identification
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What instrument is usually the most helpful when sorting Natural and Synthetic gems?
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The Microscope.
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GI10: Separation and Identification
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To confirm Double Refraction in a gem, use the:
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Dichroscope
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GI10: Separation and Identification
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What is the best type of lighting for detecting a Phenomenon like Chatoyancy or Asterism in a gem?
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Pen or Fiber-optic lighting.
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GI10: Separation and Identification
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Some key indicators that help narrow your gem identification options are:
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Color and Transparency.
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GI10: Separation and Identification
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What is the least inaccurate of Spot Reading tests?
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Average Method
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Quiz
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To look for Fire, light the gem:
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From above, with a Pen light or Fiber-optic light.
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GI10: Separation and Identification
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What are the two types of materials that can be used in place of natural and valuable gems?
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Synthetics and Imitations.
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GI11: Separating Natural Gems from Synthetics and Imitations
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What are typical Characteristic Inclusions of Melt Process Synthetics?
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Curved growth patterns, color banding or parallel growth lines, called "curved striae". Can be found using Darkfield Illumination, as well as diffused lighting.
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GI11: Separating Natural Gems from Synthetics and Imitations
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What are the best methods to separate CZ from Diamond?
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By weight or Specific Gravity. CZ is much heavier than Diamond. Also a correctly calibrated diamond tester will identify CZ.
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GI11: Separating Natural Gems from Synthetics and Imitations
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What are the typical Characteristic Inclusions of Solution-Process Synthetics?
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They can have straight or angular growth patterns (like natural gems), but the patterns are usually more uniformly spaced. Flux inclusions can also be trapped as metal droplet in a stone. These can look very similar to natural stones.
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GI11: Separating Natural Gems from Synthetics and Imitations
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Chevron Growth Pattern
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A feature of some Hydrothermal Synthetic gems that look like rows of pointed arches.
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GI11: Separating Natural Gems from Synthetics and Imitations
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What color are most Synthetic Diamonds?
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Yellow or brown, because it's extremely difficult to keep nitrogen out during crystal growth, which causes the Diamond's color.
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GI11: Separating Natural Gems from Synthetics and Imitations
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What are the Types of Diamonds?
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Type Ia: Contain Nitrogen, 95% of natural Diamonds.
Type Ib: 1% of Nitrogen colored natural Diamonds. Many Ib are synthetic yellow Diamonds. Type IIa: Little to no Nitrogen, extremely rare in nature. Most near colorless Synthetic Diamonds are IIa. Type IIb: Contain Boron, Diamonds are blue and are excellent conductors of electricity. |
GI11: Separating Natural Gems from Synthetics and Imitations
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Sedimentation
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A process in which Silica Spheres are allowed to settle and then are compressed into Synthetic Opal.
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GI11: Separating Natural Gems from Synthetics and Imitations
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Key Characteristics of Synthetic Opal
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A Snakeskin pattern or Columnar structure.
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GI11: Separating Natural Gems from Synthetics and Imitations
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Sublimation Process
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A process in which heated gases come together and crystallize. Synthetic Moissanite is the only material manufactured for jewelry use by the Sublimation Process.
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GI11: Separating Natural Gems from Synthetics and Imitations
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Paste
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Trade term for an Imitation Gem made of manmade glass. Often molded, rather than cut, leaving an uneven surface know as the "orange peel" effect. May also be warm to the touch.
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GI11: Separating Natural Gems from Synthetics and Imitations
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Slocum Stone
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A manmade Glass Opal Imitation with scattered, tinsel-like colored flakes that imitate Play-of-Color.
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GI11: Separating Natural Gems from Synthetics and Imitations
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Crust
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The surface and outermost layer of the Earth. Its thickness ranges from about 3 miles to 25 miles, may be much thicker under mountain ranges. Thinnest in the oceans.
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CS2: Gemstone Formation and Mining
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Mantle
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A layer between the Earth's crust and its core. The main bulk, and is many times thicker than the crust: about 1,790 miles thick. Some sections of the mantle are partially molten, creating conditions that can lead to periodic volcanic events at the surface.
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CS2: Gemstone Formation and Mining
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Core
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The Earth's innermost layer. Possesses a molten outer later about 1,410 miles thick, surrounding a solid central interior (mostly composed of Iron, with some Nickel) that is 1,490 miles in diameter.
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CS2: Gemstone Formation and Mining
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Magma
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General term for any molten rock. It's in constant motion and may exist only 40 miles beneath the surface.
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CS2: Gemstone Formation and Mining
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Plate
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A section of the Earth's rigid outer crust. A moving jigsaw puzzle, because they are constantly interacting with eachother.
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CS2: Gemstone Formation and Mining
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Plate Tectonics
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Study of the formation, structure, and movement of the plates of the Earth's crust. They explain the pattern of mountain ranges, volcanoes, oceans, and gem deposits across the surface.
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CS2: Gemstone Formation and Mining
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Mantle Convection
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Circulation in the Mantle that drives the movement of Earth's plates. It causes the opening of giant fissures in the Crust, in areas Geologists call Spreading Ridges.
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CS2: Gemstone Formation and Mining
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Subduction
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A process that occurs when two of the Earth's Plates collide, forcing one under the other. This melts and recycles the Crust. At the same time a new Crust is produced at the Spreading Ridges. The old one is consumed at Subduction Zones.
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CS2: Gemstone Formation and Mining
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Rock Cycle
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A constant formation and recycling process that creates new rock from old. If the rocks are deep underground, they're altered or melted by the Earth's inner forces.
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CS2: Gemstone Formation and Mining
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Igneous Rock
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Rock formed by the crystallization of molten material. The size of the rock's crystals is an indication of how long it took for it to cool. The most widespread Igneous rocks are Granite and Basalt.
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CS2: Gemstone Formation and Mining
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Erosion
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The wearing away and transport of rock materials by natural forces.
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CS2: Gemstone Formation and Mining
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Metamorphic Rock
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Rock altered by heat and pressure, or by heated fluids from magma. Marble, Ruby, Sapphire, Garnet, and Lapis Lazuli can be produced under the correct conditions. Schist is also Metamorphic rock with a distinct alignment of mineral grains.
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CS2: Gemstone Formation and Mining
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Sedimentary Rock
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Rock produced from the eroded and weathered remains of existing rocks. Some notable gems that form in Sedimentary rocks are Opal, Malachite, and Turquoise.
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CS2: Gemstone Formation and Mining
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What do Gem deposits that are found in Sedimentary Rock have in common?
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The action of water. Water moving through rocks close to the surface can dissolve and redeposit Minerals.
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CS2: Gemstone Formation and Mining
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Pneumatolysis
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Crystallization of Minerals from a gas. Topaz and Bixbite (Red Beryl) are created through this process during the final stages of cooling.
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CS2: Gemstone Formation and Mining
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Volcanic
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Pertaining to Igneous activity at the Earth's surface, where Magma erupts through a Volcano or Fissure. Gems that may have been transported by this process are: Ruby, Sapphire, Peridot, and Zircon.
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CS2: Gemstone Formation and Mining
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Xenocryst
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A "foreign crystal" that formed in unrelated rocks and was brought to the surface as a passenger in Magma. Often associated with Gem-Quality material.
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CS2: Gemstone Formation and Mining
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Pegmatite
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An Igneous Rock formed from cooling, once-molten Granite that follows fractures in its surrounding rock. Some of the biggest and best crystals in nature come from Pegmatites. These include: Tourmaline, Kunzite, Aquamarine, and other types of Beryl.
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CS2: Gemstone Formation and Mining
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Vein
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A Mineral Deposit that occupies an existing fissure or fracture in a rock. Rich purple Amethyst, Imperial Topaz, and Emeralds come from Vein Deposits that are related to Igneous activity.
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CS2: Gemstone Formation and Mining
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Intrusion
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Large mass of Igneous Rock that crystallizes underground without reaching the surface.
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CS2: Gemstone Formation and Mining
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Hydrothermal Fluid
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Hot, high-pressure solution that can dissolve, transport, and deposit Minerals from one place to another. Retains the same principle scientists use to synthesize Emeralds. Key localities of Hydrothermal Gems are Colombia and Brazil.
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CS2: Gemstone Formation and Mining
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Where is the World's only known deposit for Imperial Topaz?
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Ouro Preto, Brazil.
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CS2: Gemstone Formation and Mining
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What are two broad categories of Metamorphic Processes?
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Large-Scale Regional Metamorphism (which can affect whole mountain ranges) and Small-Scale Contact Metamorphism (Occurs in the zone surrounding intrusions of molten rock).
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Regional Metamorphism
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Changes in the Rock Type and Minerals over a wide area, caused by heat and pressure of large-scale geological events.
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CS2: Gemstone Formation and Mining
|
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Contact Metamorphism
|
Localized changes caused by an Igneous intrusion that takes place where the Magma meets the surrounding rock.
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CS2: Gemstone Formation and Mining
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Gems from Igneous Rocks
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Tourmaline, Kunzite, Beryl (All kinds), Topaz, and Corundum (As messenger gems).
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CS2: Gemstone Formation and Mining
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Gems from Metamorphic Rocks
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Garnet, Ruby, Emerald, Alexandrite, Tanzanite, Tsavorite, and Marble.
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CS2: Gemstone Formation and Mining
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Gems from Sedimentary Rocks
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Opal, Turquoise, Rhodochrosite, and Malachite.
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CS2: Gemstone Formation and Mining
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Geode
|
A spherical, often hollow, mineral-lined cavity in rock. Commonly contain concentric layers of Agate, and may have a crystal-lined cavity at the center.
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CS2: Gemstone Formation and Mining
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Primary Deposits
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Gems found in the rock that carried them to the surface. Colombian Emerald, Paraíba Tourmaline, Tanzanite, Opal, and Diamond. Primary Deposits often yield small stones.
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CS2: Gemstone Formation and Mining
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Secondary Deposits
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Gems found away from their Primary Source. Formed when gems erode from the rock they formed in and accumulate in river gravel. Typically yield gems of higher quality and durability.
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CS2: Gemstone Formation and Mining
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Heavy Minerals
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Minerals dense enough to become concentrated and separated from lighter ones by the action of surface water.
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CS2: Gemstone Formation and Mining
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Eluvial Deposit
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A Deposit where gems are eroded from the Source Rock, but remain close to its Origin, making it easier to trace back to the Primary Deposit.
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CS2: Gemstone Formation and Mining
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Alluvial Deposit
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A Deposit where gems are eroded from their Source Rock, then transported away from the source and further concentrated. Unlike Eluvials, gems can be found miles away from its Primary Deposit.
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CS2: Gemstone Formation and Mining
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Placer
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Workable Alluvial Deposit of gem materials with economic potential. Sri Lanka and Tanzania are notable Placers.
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CS2: Gemstone Formation and Mining
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Unit Cell
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The smallest group of atoms with both the Characteristic Chemical Composition and Crystal Structure of a mineral.
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CS3: Gems and Their Physical Properties
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Aggregate
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A mass of tiny, randomly oriented crystals. Can either have a Microcrystalline or Cryptocrystalline make up.
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CS3: Gems and Their Physical Properties
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Microcrystalline
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An Aggregate made up of individual crystals visible under magnification. Examples include: Nephrite, Jadeite, and Quartzite.
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CS3: Gems and Their Physical Properties
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Cryptocrystalline
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An Aggregate made up of individual crystals detectable only under very high magnification. Examples include: Chalcedony and Turquoise.
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CS3: Gems and Their Physical Properties
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Gems and Their Crystal Systems:
|
°Cubic: Diamond, Spinel, Garnet, Fluorite
°Tetragonal: Zircon °Hexagonal: Apatite, Beryl °Trigonal: Corundum, Quartz, Tourmaline °Orthorhombic: Topaz, Iolite, Tanzanite, Chrysoberyl, Peridot °Monoclinic: Kunzite, Moonstone °Triclinic: Amazonite, Rhodonite |
CS3: Gems and Their Physical Properties
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Twinning Plane
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Location of a change in Crystal Growth Direction.
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CS3: Gems and Their Physical Properties
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Liquid Inclusion
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Small pocket in a gem that fills with fluids and, sometomes, gas bubbles and tiny crystals.
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CS3: Gems and Their Physical Properties
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Two-Phase Inclusion
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A hollow cavity in a gem, usually filled with a liquid and a gas.
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CS3: Gems and Their Physical Properties
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Three-Phase Inclusion
|
A hollow cavity in a gem, filled with a liquid, a gas, and one or more crystals.
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CS3: Gems and Their Physical Properties
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Rough Shape: Tabular
|
Squat and flat, like many Corundum crystals.
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CS3: Gems and Their Physical Properties
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Rough Shape: Prism or Prismatic
|
Columnar, with 3, 4, 6, 8, or 12 parallel faces. Many Aquamarine and Tourmaline crystals are Prismatic.
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CS3: Gems and Their Physical Properties
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Rough Shape: Euhedral
|
Well formed, with sharp crystal faces, like most gems from Pegmatite pockets.
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CS3: Gems and Their Physical Properties
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Rough Shape: Anhedral
|
Lacking obvious crystal faces, like many gems that have been tumbled in rivers.
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CS3: Gems and Their Physical Properties
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Rough Shape: Striations
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Horizontal (Quartz, Corundum) or vertical (Tourmaline, Topaz) growth markings on a crystal.
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CS3: Gems and Their Physical Properties
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Rough Shape: Pyramid
|
Shape with equal triangular faces that meet in a point.
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CS3: Gems and Their Physical Properties
|
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Rough Shape: Bipyramid
|
Shape with two Pyramid back-to-back Seen in Sapphires.
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CS3: Gems and Their Physical Properties
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Selective Absorption
|
Process by which a material absorbs some components of visible light and transmits others.
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CS4: Gems and Light
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Absorption Spectrum
|
A pattern of dark vertical lines or bands shown by certain gems when viewed through a Spectroscope.
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CS4: Gems and Light
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Allochromatic
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A gem colored by Trace Elements in its Crystal Structure.
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CS4: Gems and Light
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Idiochromatic
|
A gem colored by an Element that is an essential part of its Chemical Composition.
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CS4: Gems and Light
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Transition Elements
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Elements that can selectively absorb some Wavelengths of visible light and produce color in gems.
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CS4: Gems and Light
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Fluorescence
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Emission of visible light by a material when it's stimulated by Ultraviolet Radiation.
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CS4: Gems and Light
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Charge Transfer
|
A process where the Electrons that selectively absorb light are passed back and forth between neighboring Impurity Ions.
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CS4: Gems and Light
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Intervalence Charge Transfer
|
A process where two Impurity Atoms separated by another atom can still exchange Electrons to selectively absorb light.
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CS4: Gems and Light
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Color Center
|
A small defect in the Atomic Structure of a material that can absorb light and give rise to a color.
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CS4: Gems and Light
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Pleochroism
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When a gem shows different bodycolors from different Crystal Directions.
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CS4: Gems and Light
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Interference
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Interaction of two light rays travelling in the same path.
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CS4: Gems and Light
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Diffraction
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A special kind of Interference Phenomenon that breaks up white light into its Spectral Hues.
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CS4: Gems and Light
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Treatment
|
Any Human-Controlled process, beyond cutting and polishing, that improves the Appearance, Durability, or Value of a gem.
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GI12: Detecting Gem Treatments
|
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Fracture (Fissure) Filling
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Using a Filler to conceal Fractures and improve Apparent Clarity of a gem.
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GI12: Detecting Gem Treatments
|
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Heat Treatment
|
Exposing a gem to Rising Temperatures for the purpose of changing it's appearence. Commonly Heat Treated gems are: Corundum, Tanzanite, Amethyst, Zircon, and Aquamarine.
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GI12: Detecting Gem Treatments
|
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What is the most common Corundum Treatment?
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Heat Treatment.
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GI12: Detecting Gem Treatments
|
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Discoid Fracture
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A Circular Stress Fracture that occurs when heat causes an Inclusion to Expand more than the Host Gem. Common in many heat treated stones, but especially prevalent in Corundum.
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GI12: Detecting Gem Treatments
|
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Melt Relic
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The Remains of a Mineral Inclusion that was altered by Heat Treatment. When the Melt Relic is rounded and whitish, it's called a "Snowball" Inclusion.
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GI12: Detecting Gem Treatments
|
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Bleeding
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Intense Color Concentration around a crystal that results when Rutile releases Titanium during Heat Treatment in Corundum. Also known as Broken Silk. Bleeding also makes Color Zoning in Corundum fuzzy looking.
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GI12: Detecting Gem Treatments
|
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Broken Silk
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Diffuse and Patchy remains of Rutile Needles that were partially melted by heat treatment of Corundum.
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GI12: Detecting Gem Treatments
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How Heat Treatment Affects Inclusions
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GI12: Detecting Gem Treatments
|
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Sintered Areas
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Missed or Damaged Areas when treatment impurities such as Flux solidify on the gem's surface. Can have a Dimpled or Melted appearence, and often occur near the Girdle or on the surface of Pits and Cavities.
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GI12: Detecting Gem Treatments
|
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What are methods to detect Lattice Diffusion Treatment?
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Immersed or viewed in Diffused Light. Typical signs of Lattice Diffusion include concentrated color along Facet Junctions and around the Girdle, localized color caused by uneven diffusion of Color-Causing Agents, and color Missing from some facets. Color that bleeds into Cavities and Surface-Reaching Fractures is also normal.
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GI12: Detecting Gem Treatments
|
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What is the best Liquid to test for Lattice Diffusion?
|
Methylene Iodide
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GI12: Detecting Gem Treatments
|
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What Phenomenon can Lattice Diffusion create?
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Asterism in treated Corundum, because of the presence of Titanium Oxide, which forms Rutile Needles as it cools. The result is a Shallow Six-Rayed Star.
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GI12: Detecting Gem Treatments
|
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High Pressure, High Temperature (HPHT)
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Diamond Color Modification that uses Equipment and Conditions similar to those used to grow Synthetic Diamonds. Can change the color of some Brownish Diamonds to Colorless or Near Colorless, since Brown is caused by Internal Distortion of the Diamond's Crystal Structure.
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GI12: Detecting Gem Treatments
|
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Signs of HPHT-Treated Diamond:
|
Cross-Hatched Strain Pattern that's visible under Polarized Light. Called "Tatami" because it resembles a woven floor mat. Maybe present in some Natural Diamonds, but usually more intense in HPHT-Treated Diamonds.
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GI12: Detecting Gem Treatments
|
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Hardener
|
A Chemical that treaters mix with some Resins to cause them to Solidify.
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GI12: Detecting Gem Treatments
|
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What is the most common Colored Stone that is Fracture-Filled?
|
Emeralds, they are often filled with both Natural and Manmade substances. Usually Oils or Resin, or a combination of the two. There are small differences in RI between Emerald and it's Filler, but sometimes it produces Flashes of Color when viewed under Magnification.
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GI12: Detecting Gem Treatments
|
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Flash-Effect in Emerald Fillers:
|
Occurs parallel to the Fracture Plane. Can show several Iridescent Colors simultaneously. Manmade Fillers often flash Yellow to Orange against a Dark Background, and Violet to Blue against a Bright Background. Fillers may also Fluoresce under UV Radiation. These Reactions do NOT always occur.
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GI12: Detecting Gem Treatments
|
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Common Fracture-Filled Gems:
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Emerald, Diamond, Corundum, Chrysoberyl, Tanzanite, and Tourmanline.
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GI12: Detecting Gem Treatments
|
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Signs of Fracture-Filling in Diamonds:
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°Flash Effect
°Trappes Gas Bubbles °Areas of Incomplete Filling °Flow Structure °Cloudy Filler °Crackled Web-Like Texture °Slight Hint of Color |
GI12: Detecting Gem Treatments
|
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Laser Drilling
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Using a Concentrated Beam of Laser Light to reach a Diamond's dark Inclusions and Disguise or Eliminate them. Either by using Acid or Bleaching. May be confused with Naturally Occurring Etch Channels.
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GI12: Detecting Gem Treatments
|
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Irradiation
|
Exposing a Gem to Radiation to Change or Improve its color. Commonly Irradiated Gems: Blue Topaz, Red Tourmaline, Kunzite, Smoky Quartz, and Golden Beryl. Usually, this treatment is Undetectable. But in many cases, color may fade when exposed to Heat and Light.
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GI12: Detecting Gem Treatments
|
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How to conduct a Fade Test:
|
Expose the Suspect Gem to the Light of a 250 watt bulb for 24 hours. Place the Gem close enough so that they're also affected by bulb's Heat. Stable Coloring won't fade during the test.
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GI12: Detecting Gem Treatments
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|
Naturally colored gems that may fade when exposed to Heat and Light:
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Amethyst, Rubellite (Pink Tourmaline), and Kunzite. It's important not to use the Fade Test on these stones.
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GI12: Detecting Gem Treatments
|
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Pearls and Irradiation
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Bleached Saltwater Pearls and Freshwater Cultured Pearls may also be Irradiated. The process Darkens the Bead Nucleus of Saltwater Cultured Pearls. Examining the Drill-Hole under Magnification might show a colored Bead Nucleus beneath more Transparent, nearly-colorless Nacre. Freshwater Cultured Pearls lack a Nucleus but develop an Unnatural Metallic Sheen and Strong Orient with looks Artificial.
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GI12: Detecting Gem Treatments
|
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Cat's-Eye Chrysoberyl and Irradiation
|
May be Irradiated to an Intense Honey color. Beware of that gem, because it's probably Radioactive enough to be detectable with a Geiger Counter.
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GI12: Detecting Gem Treatments
|
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Diamonds and Irradiation
|
Short Exposure in a Linear Accelerator, Exposure to Neutrons, Gamma Rays, or a Combination of the two in a Nuclear Reactor causes light yellow Diamonds to turn Green. Annealing changes Green to Brownish-Orange. Other Fancy colors may occur, but these results are not predictable. All Green Diamonds have been exposed to Radiation.
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GI12: Detecting Gem Treatments
|
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Testing to detect Irradiation in a Diamond
|
In Spectrum Testing a thin line around 594nm can indicate Irradiation. Or stones bombarded with Subatomic Particles in a Cyclotron may reveal Shallow Penetration and strong Color-Zoning around the Culet, creating an Unbrella-Shaped Pattern, when viewed under Magnification.
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GI12: Detecting Gem Treatments
|
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Type A Jadeite
|
Natural Jadeite that's Untreated or Enhanced only with a Surface Coating of Wax.
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GI12: Detecting Gem Treatments
|
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Type B Jadeite
|
Natural Jadeite that's Bleached in Acid to remove undesirable staining, then Impregnated with Wax or Polymers. May not be as durable as Type A Jade.
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GI12: Detecting Gem Treatments
|
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Type C Jadeite
|
Natural Jadeite that's Dyed and often Bleached and Impregnated with Wax or Polymers.
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GI12: Detecting Gem Treatments
|
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|
Bleaching
|
A Treatment that uses Chemicals to Lighten or remove color. If Acid-Bleached Jadeite isn't neutralized, it may release a Yellow Acid Residue.
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GI12: Detecting Gem Treatments
|
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Colorless Impregnation
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Filling of Pores and other Openings with Melted Wax, Resin, Polymer, or Plastic to Improve Appearance and Stability.
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GI12: Detecting Gem Treatments
|
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|
Other Bleached Gems
|
Tiger's-Eye and Light Colored Cultured Pearls are sometimes Bleached but not Impregnated. Detection is often Impossible.
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GI12: Detecting Gem Treatments
|
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Dyeing
|
A Treatment that adds Color or Affects Color by Deepening it, making it more Even, or Changing it. Magnification often reveals Concentrations of Dye in cracks and pores.
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GI12: Detecting Gem Treatments
|
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Lapis Lazuli and Dyeing
|
A swab dipped in Acetone may remove any Dye from Lapis Lazuli. The same can be tested with Denatured Alcohol or Diluted Hydrochloric Acid. If none of these Solvents don't work, the stone probably isn't Dyed. Dye may be harder to detect if Impregnated with Plastic or Sealed.
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GI12: Detecting Gem Treatments
|
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Jadeite and Dyeing
|
Type C Jadeite might be Dyed, might be Dyed first then Filled with a Polymer that contains a Dye. Since Dye collects in the gem's Surface Cracks, it's possible to detect with Magnification. Also can be detected by examining it's Spectrum, as Natural Green Jadeite shows Absorption Lines at 630nm-655nm-691nm. While Dyed Green Jadeite can show a Single Broad Band in the area occupied by those Three Lines.
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GI12: Detecting Gem Treatments
|
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Chalcedony and Dyeing
|
Very Frequently Dyed. Spectrum, Color Filter, and Fluorescence are Key Tests that can separate Dyed Chalcedony from other gems, such as Chrysocolla-in-Chalcedony and Chrysoprase. Agate is also usually Dyed, as well as Opaque Jasper to Imitate Lapis Lazuli, the difference can be determined by Chalcedony's Dull-Conchoidal Fracture and Lapis Lazuli's Granular Fracture.
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GI12: Detecting Gem Treatments
|
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Quartz and Dyeing
|
Quartzite can be Dyed any color. Usually Green to Imitate Jadeite. Tiger's-Eye Quartz may also be Dyed Unnatural colors. Magnification reveals Dye Concentrations in their Fractures.
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GI12: Detecting Gem Treatments
|
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Beryl and Dyeing
|
Green Beryl may be Dyed to give it the color of Emerald. Under Magnification, you can see Dye in the gem's Fractures. Hot Point will also help detect this Treatment.
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GI12: Detecting Gem Treatments
|
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Howlite and Dyeing
|
Howlite is commonly Dyed Blue to Imitate Turquoise, and at time, even Lapis Lazuli. If the Blue color doesn't already look Unnatural, using a Color Filter can make the stone Glow Pinkish through the Dye.
|
GI12: Detecting Gem Treatments
|
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|
Pearls and Dyeing
|
Freshwater and Saltwater Cultured Pearls may undergo a Treatment called Pinking after being Bleached. The Pearls are given a Pink Tint that many Consumers prefer to plain white. Many Poor Quality Chinese Freshwater Pearls are Dyed with Obviously Unnatural colors. Pearls Dyed Black can have Dye swabbed off with a light Nitric Acid Solution, shortly should be Neutralized to avoid damaging the Pearl.
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GI12: Detecting Gem Treatments
|
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Pinking
|
Tinting a Cultured Pearl with a Red Dye.
|
GI12: Detecting Gem Treatments
|
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|
Surface Modification
|
Altering a Gem's Appearance, by applying a Backing, Coating, or Coloring Agent, like Paint. Coated CZ is marketed under the name Tavalite. Aqua Aura involves Depositing a thin, almost transparent layer of Gold on Quartz or Topaz. This gives the gem an Iridescent Blue or Blue-Green color. Pearls may have a Colorless Polymer on their surface to Improve Luster.
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GI12: Detecting Gem Treatments
|
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|
Sugar Treatment
|
Soaking an Opal in a Hot Sugar Solution and then in Sulfuric Acid to Darken it and bring out its Play-of-Color. Dark areas may look like Pepper. Done on more Porous Stones and easily detectable.
|
GI12: Detecting Gem Treatments
|
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|
Smoke Treatment
|
Heating a Wrapped Opal until Smoke or Ash Penetrates its Surface to Darken it and bring out its Play-of-Color. Have an overall Dark and Patchy look. Confined to a shallow layer and often Superficial. Also easy to detect.
|
GI12: Detecting Gem Treatments
|
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Examples of Gems and what they're treated for
|
°Color : Tanzanite
°Clarity : Emerald °Inclusions : Amber °Luster : Jadeite °Durability : Turquoise |
CS6: Treatments
|
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Oxidizing Environment
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An Oxygen-Rich Environment that surrounds a gem during Heat Treatment, causing it to absorb Oxygen.
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CS6: Treatments
|
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Reducing Environment
|
An Oxygen-Poor Environment that surrounds a gem during Heat Treatment, causing it to lose Oxygen. Usually surrounded by gases other than Oxygen, like Nitrogen or a Hydrogen-Nitrogen Mixture, or by Substances like Sugar, Oil, or Glycerin.
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CS6: Treatments
|
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Quench Crackling
|
A Rapid Heating and Cooling Process that produces Fractures in a stone so it will accept Dye. This may also Imitate Fingerprints that are found in Natural Rubies.
|
CS6: Treatments
|
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Resin
|
A Clear, Viscous Substance that's used to Fill Fractures in gemstones.
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CS6: Treatments
|
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Polymer
|
A Liquid Filling Material that's very Durable when it dries.
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CS6: Treatments
|
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|
Commonly Heat Treated Gems
|
95% of Corundum, virtually all Tanzanite, Zircon, Topaz, Aquamarine, and Amber.
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CS6: Treatments
|
|
|
Written Information On Dyeing Gems Dates Back To About:
|
200 BC.
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CS6: Treatments
|
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|
Heat Can Lighten An Amethyst's Purple By:
|
Causing Changes in Color Centers.
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CS6: Treatments
|
|
|
Creating Asterism With Heat Treatment Is Most Common in:
|
Synthetic Corundum.
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CS6: Treatments
|
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|
What Coloring Agents Do Treaters Use During Lattice Diffusion To Create A Shallow Layer Of Blue Color In Corundum?
|
Titanium Oxide and Iron Oxide.
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CS6: Treatments
|
|
|
How Deep Is The Layer That Lattice Diffusion With Titanium Or Chromium Creates In Corundum?
|
.01mm to .50mm
|
CS6: Treatments
|
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|
What Agent Can Create a Shallow Layer Of Asterism When It's Introduced Below The Surface Of A Corundum Cabochon By Lattice Diffusion?
|
Titanium Oxide
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CS6: Treatments
|
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|
For Effective Clarity Enhancement, The Material Used To Fill A Gem's Fractures Must Have Nearly The Same:
|
Refractive Index as the gem.
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CS6: Treatments
|
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|
Gems That Tend To Be Stable After Irradiation:
|
Blue Topaz (May have residual Radioactivity), Irradiated Light Tourmaline becomes a Stable Pink or Red, Irradiated Beryl may become a Stable Golden color that is also Undetectable.
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CS6: Treatments
|
|
|
The Zachery Method Is A Treatment Applied To:
|
Turquoise that is Treated to take on a Better Polish and appear Less Porous. Similar to those of Untreated Better Quality Turquoise.
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CS6: Treatments
|
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|
Heat Treatment In A Reducing Environment:
|
Deepens Blue color in Sapphire, and makes Rubies and Pink Sapphires appear more Purple.
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CS6: Treatments
|
|
|
What Are The Most Popular Transparent Red-To-Pink Natural Gems?
|
Corundum, Garnet, and Tourmaline. Sometimes Spinel.
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GI13: Separating Red, Pink, and Purple Gems
|
|
|
Red Stones That Don't Have A Commercially Produced Synthetic Version
|
Tourmaline, Topaz, Garnet, and Spodumene.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
"Comet-Tail" Inclusion
|
Inclusions that occur in Flux Synthetics when small Flux particles appear to stream out behind larger Flux Droplets. Usually in Synthetic Corundum.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Detecting Platinum Inclusions in Synthetics
|
Make sure you examine any Plate - Like Inclusions under Reflected Light to make the platelets look reflective, and Darkfield Light which makes them look darker and Opaque.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
What are some producers of Pulled Pink Synthetic Sapphires?
|
Union Carbide, Kyocera, and some other Russian companies. These Sapphires are also known as "Ti-Sapphires", because they are colored by Titanium. Originally produced for tech applications, like lasers.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Who are past and present Manufacturers of Flux-Grown Synthetic Rubies?
|
Chatham, Kashan, J.O. Crystal, Knischka, Lechleitner, Douros, and some other Russian producers. Some of these companies no longer produce synthetic gems, but they still exist in the market.
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GI13: Separating Red, Pink, and Purple Gems
|
|
|
How do Flux Rubies resemble Natural Rubies?
|
Unlike Flame-Fusion material, Flux crystals have Straight and Angular growth, instead of Curved Striae. They also have a wide variety of inclusions, much like Natural Rubies.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Kashan Ruby
|
Fine, tiny Flux particles arranged in parallel rows. Gemologists call them "rain". Delicate strings of Flux that curl back on themselves to produce a Hairpin-Like structure. As well as Comet Tails. Can have wispy white Flux Veils.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Chatham Ruby
|
Often contain Platinum inclusions, that are larger than other Synthetics. They use Synthetic Corundum Seeds, but there's rarely any trace of of them after the stones are fashioned.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Knischka Ruby
|
Has much smaller Platinum inclusions than Chatham Synthetic Rubies. Contain wispy white Flux Veils and Negative Crystals filled with Flux.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Ramaura Ruby
|
Contain small Platinum inclusions like Knischka Rubies. Capable of Two-Phase Flux Globules or Rods, together with healed fractures and Wispy Veils. While it can resemble a Natural Ruby, the Flux inclusions are a distinctive Orange-Yellow color, may appear Colorless or White in small pockets.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Douros Ruby
|
No reported Platinum inclusions. However, Flux inclusions are distinctly Orange-Yellow, but may appear Colorless or White in small pockets.
|
GI13: Separating Red, Pink, and Purple Gems
|
|
|
Lechleitner Ruby
|
No reported Platinum inclusions. Uses a Pre-Fashioned Seed that makes up most of the finished gem, which means their Rubies are basically Thin Flux Overgrowth on Natural or Flame-Fusion Synthetic Seeds. It's often hard to see the Seed and Overgrowth, which isn't usually any more than 1mm-2mm deep.
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GI13: Separating Red, Pink, and Purple Gems
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What is a Garnet's Characteristic Iron Absorption Spectrum?
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Three strong Bands in the Green and Yellow Spectrum:
Almandine - 505•527•575 Pyrope - 505, and if there's Chromium: 520-620 Band |
GI13: Separating Red, Pink, and Purple Gems
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Commercial Market
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Market Sector where average quality Gemstones are used in Mass-Market Jewelry.
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CS7: The Colored Stone Market
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Cut (Parcel)
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A Gem Dealer's term for a random sample from a Parcel of Gemstones, often used to assess the Parcel's overall quality.
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CS7: The Colored Stone Market
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Calibrated Sizes
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Gemstone sizes cut to fit standard mountings.
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CS7: The Colored Stone Market
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Certificate of Origin
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A Document that indicates a Stone's Geographic Origin, based on its inclusions and Trace Element Chemistry.
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CS7: The Colored Stone Market
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Custom-Made Jewelry
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A Unique piece designed and created for a particular customer, often around specially chosen stones.
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CS7: The Colored Stone Market
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Cutter
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A Manufacturer who produces Faceted stones, Cabochons, or Carvings.
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CS7: The Colored Stone Market
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Cutting Center
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A City, Region, or Country with a large number of Gemstone Manufacturers.
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CS7: The Colored Stone Market
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Facet Grade
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Gemstone rough that's Transparent enough and of high enough Quality to produce Faceted Gems.
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CS7: The Colored Stone Market
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Free-Size
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Non-Standard cutting, usually applied to Large, Important Stones for use in Expensive Jewelry where standard size is not a consideration.
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CS7: The Colored Stone Market
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High-End Market
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Market Sector where fine quality, Expensive Gemstones are used in Unique, Handcrafted Jewelry pierces.
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CS7: The Colored Stone Market
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High Grading
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In Mining terms, Theft of a Mine's production by its workers.
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CS7: The Colored Stone Market
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Lot Price
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A Discounted Price for buying an entire Parcel or a substantial part of it.
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CS7: The Colored Stone Market
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Middle Market
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Market Sector where Better-Quality Gemstones are used in Well-Finished, moderately priced Jewelry Pieces.
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CS7: The Colored Stone Market
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Mine Lot (Mine Run)
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A Mixture of Gem Qualities that represents Unsorted Production from a particular Mine.
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CS7: The Colored Stone Market
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Origin
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The Geographical Place where a Gem was Mined.
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CS7: The Colored Stone Market
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Parcel
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A Quantity of Stones, sometimes of similar Size and Quality, perhaps from a Single Mine, but often various Sources, that's offered for sale together.
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CS7: The Colored Stone Market
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Pick Price
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A Premium Price for Selecting Stones from a Parcel.
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CS7: The Colored Stone Market
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Source
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A Gem-Producing area, or a particular Mine in that area.
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CS7: The Colored Stone Market
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Wholesaler
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A Company or Individual that supplies Gems to Jewelry Manufacturers and Retailers.
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CS7: The Colored Stone Market
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You would identify a Transparent, Deep Pink, DR gem with an RI of 1.62 to 1.64 and a Birefringence of .020 as:
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Pink Tourmaline (Also known as Rubellite)
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GI13: Separating Red, Pink, and Purple Gems
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You would identify a Transparent, Red-Orange, SR stone with an RI of 1.72 and a Chromium Spectrum as:
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Red Spinel
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GI13: Separating Red, Pink, and Purple Gems
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You would identify an Opaque, Orange-Red gem with a wavy, Fibrous Structure and Birefringence Blink as:
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Calcareous Coral
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GI13: Separating Red, Pink, and Purple Gems
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One of the best ways to determine if a Pink stone is Tourmaline or a Topaz is to observe:
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Birefringence or Heft (Topaz is heavier than Tourmaline).
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GI13: Separating Red, Pink, and Purple Gems
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The Characteristics that separate Sugilite from Charoite are RI and:
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Appearance
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GI13: Separating Red, Pink, and Purple Gems
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What determines a Sapphire's value?
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Color, Cut, Clarity, Size, and Treatments.
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CS13: Blue Sapphire
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Qualities of a High Valued Sapphire
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Velvety Blue to Violetish Blue, in medium to medium-dark tones. Strong Vivid Saturation without darkening the stone.
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CS13: Blue Sapphire
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Basaltic Sapphire
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Medium-Good quality color. Generally richer in Iron from Non-Basaltic sources, which makes them darker and can reduce their value. Regions include: Cambodia, Thailand, and Australia.
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CS13: Blue Sapphire
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Non-Basaltic Sapphire
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Form under a variety of conditions, in Kashmir they occur in Marble and Pegmatites, in Yogo Gulch (Montana) they come from a rare Igneous Rock, while in Sri Lanka and Mogok (Burma) Metamorphism is associated with their Sapphires.
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CS13: Blue Sapphire
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"Kashmir" Sapphire
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Violetish-Blue to pure Blue Hue, with moderately strong to vivid saturation and medium-dark tone. Minute Inclusions make them appear Velvety in Luster. Regarded as the finest qualtiy of Sapphire.
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CS13: Blue Sapphire
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"Burmese" Sapphire
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Slightly Violetish-Blue to Blue Hue, with moderately strong to vivid Saturation and medium to dark Tone. More intense than Kashmir Sapphires, without a Velvety Luster. Somewhat Inky under Incandescent Light and a Royal Blue color. Considered very-fine-quality Sapphires.
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CS13: Blue Sapphire
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"Ceylon" and "Sri Lankan" Sapphire
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Violetish-Blue to Blue Hue, Slightly Greyish to strong Saturation and light to medium-light Tone. Have greater Brilliance than darker-toned Sapphires.
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CS13: Blue Sapphire
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"Pailin" and "Cambodian" Sapphire
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Sapphires that are Violetish-Blue to Very Slightly Greenish-Blue,with medium to dark Tone. Look best when fashioned into smaller stones, so they don't look too dark.
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CS13: Blue Sapphire
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"Kanchanaburi" Sapphire
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Blue to Slightly Greenish-Blue, with light to dark Tone. Less Saturated stones look Greyish. Might have a Milky appearance. Similar to Sri Lankan Sapphires in color, but not as Brilliant.
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CS13: Blue Sapphire
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"Thai" Sapphire
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Violetish-Blue to Slightly Greenish-Blue, medium to dark Tone. Often described as Inky-Blue or Blue-Black.
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CS13: Blue Sapphire
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"Australian" Sapphire
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Violetish-Blue to Very Strongly Greenish-Blue, with medium-dark to very dark Tone. Often show a strong Greenish-Blue Pleochroism. Described as an Inky-Blue.
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CS13: Blue Sapphire
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Types of Inclusions found in Sapphires:
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Silk (Rutile Needles), Boehmite Needles, Included Crystals, Fingerprint Inclusions, Growth Zoning, Color Zoning and Banding.
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CS13: Blue Sapphire
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Heat Treatment in Sapphires
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Treated in temperatures from ~850°F to 3500°F (450°C to 1900°C). They remain in this temperature anywhere from less than one hour to 14 days.
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CS13: Blue Sapphire
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Geuda
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Milky, Greyish, or Brownish Corundum that can be treated to a fine Blue Color. Makes up a significant portion of the Commercial-Quality Sapphire Market.
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CS13: Blue Sapphire
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Dhun
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Smoky Corundum that turns Blue when Treated. More efficient to treat than Geuda. Makes up a significant portion of the Commercial-Quality Sapphire Market.
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CS13: Blue Sapphire
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What's the biggest Market for Sapphire?
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The U.S. is the biggest Market for Sapphire. Other significant purchasers include: Japan, Germany, Switzerland, Great Britain, and Taiwan.
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CS13: Blue Sapphire
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Largest Cutters of Sapphires
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Thailand, India, and Sri Lanka.
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CS13: Blue Sapphire
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Kashmir's most important Sapphire production period was from:
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1881 to 1887
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CS13: Blue Sapphire
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When did Madagascar become a significant source of Blue Sapphire?
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1990s
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CS13: Blue Sapphire
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Most fine Sapphires over 100cts. come from:
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Sri Lanka
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CS13: Blue Sapphire
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Blue Sapphire's Pleochroic colors are typically:
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Slightly Greenish-Blue and Slightly Violetish-Blue.
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CS13: Blue Sapphire
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How big is The Star of India?
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563cts.
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CS14: Fancy Sapphire And Phenomenal Corundum
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Padparascha Sapphire
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Intensely Saturated, and a range of color between light to medium Pinkish-Orange to Orange-Pink. Traces of Iron and Chromium, and even Color Centers cause Padparascha's unique Hues.
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CS14: Fancy Sapphire And Phenomenal Corundum
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