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332 Cards in this Set
- Front
- Back
Abrasion (Abr)
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A series of minute scratches or pits along the facet junctions of a fashioned diamond; gives the edges a white or fuzzy appearance.
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Adamantine luster
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The highest degree of luster possible in a transparent material. (Assignment 8)
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Aggregate
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A solid mass of individual, randomly oriented crystals, intergrown or held together by a natural binding agent. (Assignment 7)
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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. (Assignment 5)
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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. (Assignment 8)
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Angle of reflection
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The angle between the normal and a reflected ray of light. (Assignment 8)
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Annealing
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Using heat to stabilize irradiated color in gemstones. (Assignment 12)
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Appraisal
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An estimation of the value of an article, usually for insurance purposes. (Assignment 1)
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Average girdle diameter
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The result achieved by adding the smallest and largest diameter measurements of a round brilliant and dividing by two. (Assignment 14)
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Bast
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Frosted rough diamond. "Bark" in Dutch. (Assignment 9)
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Bearded Girdle (BG)
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Minute or minor feathers that run perpendicular to a bruted girdle; referred to more generally as feathers in the girdle. (Assignment 10)
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Belly
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The slightly curving center of the long side of a pear, marquise, heart, or oval. (Assignment 16)
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Beneficiation
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A commitment to reserve a portion of the resources derived from any country for the economic development of that country. (Assignment 3)
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Best Practices Principles (BPP)
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De Beers' formalized commitment of itself and its sightholders to the highest ethical standards. (Assignment 3)
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Blemish
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Clarity characteristic that's confined to the surface of a polished gemstone. (Assignment 10)
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Block caving
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Underground mining that involves building a concrete-lined tunnel under an ore deposit, then collecting the ore through openings in the liner. (Assignment 6)
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Blocking
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Placing the first 17 or 18 facets on a diamond. (Assignment 9)
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Bow-tie
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A dark area across the center of an elongated brilliant cut. (Assignment 16)
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Brick-and-mortar retailer
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A traditional store consisting of walls and a fixed location. (Assignment 3)
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Brightness
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The effect of all the diamond's internal and external reflections of white light. (Assignment 8)
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Brilliant cut
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A cutting style in which triangular and kite-shaped facets radiate from a gem's center toward its girdle. (Assignment 16)
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Brillianteering
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Placement and polishing of the star and upper and lower girdle facets. (Assignment 9)
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Bruise (Br)
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A tiny area of impact accompanied by very small, root-like feathers visible at 10X magnification; typically occurs at a facet junction. (Assignment 10)
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Bruting
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Forming the basic face-up outline of a diamond to prepare it for faceting. (Assignment 9)
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Bulk sampling
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Large-scale character sampling. (Assignment 5)
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Burn (Brn)
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Hazy surface area that results from excessive heat during polishing or occasionally from a jeweler’s torch. (Assignment 10)
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Cavity (Cav)
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An opening on the surface that occurs when part of a feather breaks away, or when a crystal drops out or is forced out, typically during polishing. (Assignment 10)
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Central Selling Organisation (CSO)
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An agency designed to purchase, sort, evaluate, and sell rough diamonds. (Assignment 2)
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Character sampling
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Testing for the size, shape, clarity, and color of the diamonds in a deposit. (Assignment 5)
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Characteristic color
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The basic face-up color of a colored diamond. (Assignment 13)
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Chemical vapor deposition (CVD)
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An industrial process adapted to allow growth of synthetic diamond from carbon-rich gas in thin layers onto a silicon or diamond surface. (Assignment 19)
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Chip (Ch)
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A shallow opening caused by damage to the stone's surface; typically occurs at a girdle edge, facet junction, or culet. (Assignment 10)
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Clarity characteristic
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Internal or external feature of a gemstone that helps determine its quality and establish its identity. (Assignment 10)
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Cleavage plane
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Plane parallel to a possible crystal face, where a diamond can split cleanly when struck. (Assignment 7)
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Cleaver
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A person who cleaves, or splits, a diamond along a cleavage plane. The cleaver might also be responsible for planning the fashioning of a polished gem. (Assignment 9)
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Cleaving
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Dividing a diamond into two or more pieces along a cleavage plane. (Assignment 9)
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Cloud (Cld)
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Many tightly grouped pinpoints that might be too small to distinguish individually at 10X but together have a hazy appearance. (Assignment 10)
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Color center
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Structural defect that influences an object's absorption of light and can cause its color. (Assignment 12)
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Colored diamonds
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Yellow, brown, and gray diamonds with more color than the Z masterstone, or that exhibit any other color face-up. (Assignment 12)
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Conflict diamonds
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Diamonds used to finance violence and terror. (Assignment 3)
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Consignment
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A selection of goods loaned to a dealer by another wholesaler or manufacturer. (Assignment 20)
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Core
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Earth's innermost layer. (Assignment 4)
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Covalent bond
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A chemical bond formed by two atoms sharing electrons. (Assignment 7)
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Craftsmanship
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The care that goes into the fashioning of a polished diamond, as confirmed by its finish. (Assignment 15)
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Cratons
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Ancient, large, and stable parts of the earth's continental crust. (Assignment 4)
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Critical angle
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Angle between the normal and the maximum angle of refraction, which is the largest angle at which rays inside the diamond can escape. (Assignment 8)
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Cross worker
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A person who performs the cross-working operations during diamond polishing; sometimes called a cross cutter. (Assignment 9)
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Cross working
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Placing the bezel and pavilion facets on round and fancy shapes. Sometimes combined with blocking, especially on smaller stones. Also called cross cutting. (Assignment 9)
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Crown angle
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The angle formed by the bezel facets and the girdle plane. (Assignment 14)
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Crown height percentage
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The distance from the girdle plane to the table, expressed as a percentage of average girdle diameter. (Assignment 14)
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Crust
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The surface and outermost layer of the earth. (Assignment 4)
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Crystal
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Solid matter with atoms arranged in a regular, repeating pattern. (Assignment 7)
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Crystal (Xtl)
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A mineral crystal contained in a diamond. (Assignment 10)
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Crystal planes
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Internal directions parallel to a mineral's unit cell surfaces. (Assignment 7)
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Crystal shape (form)
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Geometric shape of a well-formed crystal. (Assignment 7)
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Crystal structure (lattice)
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Regular, repeating arrangement of atoms in a mineral. (Assignment 7)
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Crystal systems
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Categories of crystals based on their symmetry and internal structure. (Assignment 7)
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Crystalline
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Composed of crystals or related to crystals. (Assignment 7)
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Culet size
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The size of the facet at the bottom of the diamond where the pavilion mains meet. (Assignment 15)
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Cuttable rough
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Diamond rough with good enough size, shape, clarity, and color to produce a polished stone suitable for use in jewelry. (Assignment 5)
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Cutting center
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A city, region, or country with a large number of gemstone manufacturers. (Assignment 3)
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Cutting style
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The arrangement of a gem's facets. (Assignment 16)
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Darkfield illumination
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Lighting of a diamond from the side against a black, non-reflective background. (Assignment 10)
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Dense media separation
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A recovery process that separates diamonds from lighter material. Also called heavy media separation. (Assignment 6)
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Depth of field
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The distance that's clear and sharp above and below a point you focus on with a magnifier. (Assignment 10)
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Design
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A diamond's physical shape, including its proportions and durability, determined by decisions made during the fashioning process. (Assignment 15)
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Diamantaire
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A knowledgeable, experienced, and successful person, usually a dealer or manufacturer, in the diamond trade. (Assignment 20)
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Diamond pipeline
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The path diamonds followed from the mine to the consumer. (Assignment 2)
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Diamond simulant
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Any material that is not diamond or synthetic diamond, but which imitates a diamond's appearance and is used in its place. (Assignment 18)
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Digger
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An independent diamond prospector. (Assignment 2)
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Digging out
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A weight-retention method where the cutter leaves more girdle thickness to allow for later removal of clarity characteristics around the girdle. (Assignment 14)
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Dispersion
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An optical property that's the difference between the RI values of specific violet and red wavelengths of visible light for a given material. (Assignment 8)
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Dop
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A holder that secures a diamond during sawing, bruting, or polishing. (Assignment 9)
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Dop Burn (Dop)
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A surface burn caused by excessive heat at the location where the dop touches the diamond. (Assignment 10)
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Doublet
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Two separate pieces of material fused or cemented together to form a single assembled stone. (Assignment 18)
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Doubling
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The appearance of double images of a gemstone's facet junctions on the side opposite the viewer. (Assignment 7)
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Doubly refractive (anisotropic) Doubly refractive (anisotropic)
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Possessing different physical or optical properties in different crystal directions. (Assignment 7)`
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Drift
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A horizontal tunnel drilled through a diamond pipe. (Assignment 6)
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Dry diggings
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A prospector's term for diamond deposits away from water. (Assignment 2)
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Electronic retailer
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Business that sells to consumers via television cable, phone line, or satellite. (Assignment 3)
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Emplacement
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A geologic process that delivers materials (sometimes diamonds) to the surface. (Assignment 4)
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Etch Channel (EC)
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An angular opening that starts at the surface and extends into the stone, often with striations perpendicular to its length. (Assignment 10)
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Extra Facet (EF)
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A small facet that's not required by the cutting style, placed without regard for the diamond's symmetry; most often found near the girdle. (Assignment 10)
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Eye-visible
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Visible to the unaided eye, without magnification. (Assignment 11)
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Face-down (or table-down)
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A position that orients a gemstone's pavilion toward the viewer. (Assignment 13)
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Face-up
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A position that orients a gemstone's crown facets and table toward the viewer. (Assignment 10)
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Face-up (or table-up)
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A position that orients a gemstone's crown toward the viewer. (Assignment 13)
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Fancy cut
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Any gemstone shape other than a standard round brilliant. (Assignment 16)
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Feather (Ftr)
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General trade term for a break in a gemstone. Often white and feathery in appearance. (Assignment 10)
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Finish
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The quality of the polish and precision of the cut of a fashioned gemstone. (Assignment 15)
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Fire
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The flashes of color you see in a polished diamond. (Assignment 8)
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Flash effect
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A flash of changing color seen in a fracture-filled diamond when you look parallel to the filled inclusion and rock the diamond back and forth under magnification. (Assignment 10)
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Fluorescence
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Emission of visible light by a material when it's exposed to ultraviolet radiation. (Assignment 12)
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Foilback
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Gemstone or simulant with a thin metallic foil or mirroring film applied to its pavilion. (Assignment 18)
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Foss
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Irregular furrow or groove in the surface of a diamond, characteristic of diamond crystals in the gray color range. (Assignment 9)
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Four-point diamond
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A diamond with the table parallel to a possible cubic face. (Assignment 9)
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Fracture filling
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Treatment that involves injecting a molten glass substance into a diamond's surface-reaching feathers or laser drill-holes. (Assignment 10)
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French tips
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A faceting style that replaces the large bezel facets at the points of marquises, pears, and hearts with star and upper half facets. (Assignment 16)
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Girdle thickness
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The width of a fashioned gem's girdle. (Assignment 14)
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Girdle thickness percentage
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Girdle thickness expressed as a percentage of average girdle diameter. (Assignment 15)
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Glassie
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A well-shaped, transparent, octahedral diamond crystal with sharp, square edges. (Assignment 7)
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Gletz
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Dutch term for a feather in a diamond. (Assignment 9)
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Glide plane
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Crystal distortion caused during growth when one part of the lattice is offset in relation to the rest. (Assignment 7)
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Grade-setting characteristics
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Inclusions or blemishes that establish the clarity grade of a diamond. (Assignment 11)
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Grain Center (GC)
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A type of internal graining that consists of a small, concentrated area of crystal distortion; can be white or dark, and might appear thread-like or pinpoint-like. (Assignment 10)
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Graining (grain lines)
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Visible, shadow-like lines in a diamond caused by irregularities in the crystal structure. (Assignment 7)
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Graphitization
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Graphite formation around a diamond's mineral inclusions and feathers that results from the extreme conditions of HPHT processing. (Assignment 19)
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Gravity sorting
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Separating heavier materials (diamonds) from a test sample. (Assignment 5)
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Grease belt
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An apparatus that uses diamonds' affinity for grease to separate them from other minerals. (Assignment 6)
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Habit
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Characteristic crystal shape of a specific mineral. (Assignment 7)
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Half-life
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The length of time required for half of a group of atoms of a particular type (radioactive) to decay into another type (non-radioactive). (Assignment 19)
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High pressure, high temperature (HPHT)
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Diamond synthesis method that mimics the pressure and temperature conditions that lead to natural diamond formation. (Assignment 19)
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Igneous Rock
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A category of rocks formed from a molten state. (Assignment 4)
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Improvables
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Diamonds that can be repolished to improve their clarity to a VVS1 or VVS2 grade. (Assignment 17)
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Inclusion
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Clarity characteristic totally enclosed in a polished gemstone or extending into it from the surface. (Assignment 10)
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Indented Natural (IN)
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A portion of the rough’s original surface, or skin, that dips below the polished diamond’s surface at 10X. (Assignment 10)
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Indicator minerals
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Minerals formed together with diamonds at great depths and brought to the surface by the same kimberlites or lamproites. (Assignment 5)
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Industrial rough
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Diamond rough suitable for use in tools, drills, abrasives, and other industrial applications. (Assignment 5)
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Internal Graining (IG)
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Lines, angles, or curves that might appear whitish, colored, or reflective or affect transparency at 10X; caused by irregularities in crystal growth. (Assignment 10)
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Internal laser drilling (ILD)
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A clarity treatment that uses a laser to expand an existing cleavage or create a new one, allowing the introduction of a bleaching solution. (Assignment 19)
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Internal Laser Drilling (ILD)
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Laser drilling within a diamond that doesn’t reach the surface. (Assignment 10)
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Irradiation
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Exposure of a material to radiation; causes color change in diamonds. (Assignment 19)
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Kaps
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Dutch term for a diamond that has been cleaved, split, or sawn, but not fashioned. (Assignment 9)
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Kerf
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A notch scratched into diamond rough to prepare it for cleaving. (Assignment 9)
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Kimberley Process (KP)
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Diamond industry program designed to ensure that diamonds crossing international borders are legitimate and do not fund civil conflict or terrorism. (Assignment 3)
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Kimberlite
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An igneous rock that transports diamonds to the surface. (Assignment 4)
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Knot (K)
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An included diamond crystal that extends to the surface after fashioning. (Assignment 10)
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Lamproite
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An igneous rock, rarer than kimberlite, that transports diamonds to the surface. (Assignment 4)
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Laser Drill-hole (LDH)
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A tiny, surface-reaching tunnel produced by a laser light beam. (Assignment 10)
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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. (Assignment 19)
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Laser Manufacturing Remnants (LMR)
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Internal fractures (inclusions) or surface grooves (blemishes) created as a result of laser marking or manufacturing. (Assignment 10)
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Length-to-width ratio
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A numerical expression of the relationship between the length and width of a fancy cut, where the value for width is one. (Assignment 16)
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Linear accelerator
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A machine used to accelerate electrons to high energy along a straight path. (Assignment 19)
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Lizard Skin (LS)
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Wavy or bumpy area on the surface of a polished diamond. (Assignment 10)
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London Diamond Syndicate
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A group of diamond merchants that united in 1890 to buy and sell rough diamonds. (Assignment 2)
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Lot price
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A discounted price for buying an entire parcel, or a substantial part of it. (Assignment 20)
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Lower half length percentage
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The length of the lower half facets expressed as a percentage of the total distance between the girdle and the culet. (Assignment 15)
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Luster
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The appearance of a material's surface in reflected light. (Assignment 8)
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Macle
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A flat, triangular twinned diamond crystal. (Assignment 7)
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Mantle
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Layer between the earth's crust and its core. (Assignment 4)
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Marine deposit
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Secondary diamond deposit carried by rivers or streams to the ocean floor or shoreline. (Assignment 5)
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Master-eye effect
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The optical illusion that causes the ungraded diamond to appear either lighter or darker than the masterstone, depending on which side it's on. (Assignment 13)
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Masterstones
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A set of color-comparison diamonds that defines GIA diamond color grades in the normal (D-to-Z) range. (Assignment 13)
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Matching tray
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A grooved, white, non-reflective tray used for matching sets of stones. (Assignment 20)
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Memo
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Buying agreement where a dealer entrusts merchandise to a customer for inspection and approval without requiring immediate payment. (Assignment 20)
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Metamorphic rock
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A category of rocks that have been altered by heat and pressure. (Assignment 4)
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Microdiamond testing
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Screening for the presence of tiny diamonds in a sample. (Assignment 5)
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Mixed cut
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A cutting style that combines step-cut and brilliant-cut facets. (Assignment 16)
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Naif
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The natural, unpolished surface of a rough diamond. (Assignment 9)
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Natural (N)
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A portion of the original surface, or skin, of a rough diamond left on a fashioned stone; usually on or near the girdle. (Assignment 10)
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Natural Radiation Stain
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Green or brown patch of color, usually seen around the girdle on the surface of a cut diamond. Typically a blemish, but can be an inclusion if it extends into the stone. (Assignment 10)
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Near-gem
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Diamond rough whose color and clarity is such that it can be either polished or used industrially, depending on market conditions. (Assignment 6)
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Needle (Ndl)
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A long, thin crystal that looks like a tiny rod at 10X. (Assignment 10)
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Nick (Nck)
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A small notch on a facet junction with no readily apparent depth at 10X, usually along the girdle edge or at the culet. (Assignment 10)
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Normal
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An imaginary line perpendicular to the point where a ray of light strikes the surface. (Assignment 8)
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Normal color range
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Range of diamond colors from colorless to light yellow, brown, and gray, also called the D-to-Z range. (Assignment 12)
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Octahedron
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A form with eight equal triangular sides. (Assignment 7)
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Old European cut
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An early brilliant cut with a circular girdle. (Assignment 9)
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Old-mine cut
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An early cushion-shaped brilliant with a high crown, deep pavilion, and 58 facets including a large culet. (Assignment 9)
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Open-pit mining
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Removal of mineral-bearing ore from a large surface excavation. (Assignment 6)
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Ore grade
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Concentration of diamond in a potentially mineable deposit.(Assignment 5)
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Overburden
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Sand, gravel, or rock that covers a diamond pipe. Must be removed to reach diamond-bearing ore. (Assignment 6)
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Painting
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A weight-retention method that adjusts the angles of some facets to allow portions of a diamond's girdle to be thicker. (Assignment 14)
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Parcel
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A quantity of stones, sometimes of similar size and quality, packaged together for sale or storage. (Assignment 20)
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Patch of Color (Patch)
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Naturally occurring radiation stain left on a polished diamond. Typically a blemish, but can be an inclusion if it extends into the stone when viewed at 10X. (Assignment 10)
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Pattern
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The relative size, arrangement, and contrast of bright and dark areas that result from a diamond's internal and external reflections. (Assignment 8)
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Pavilion angle
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The angle formed by the pavilion mains and the girdle plane. (Assignment 15)
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Pavilion bulge
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Outward curve of the pavilion facets of a step-cut diamond. (Assignment 16)
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Pavilion depth percentage
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The distance from the girdle plane to the culet, expressed as a percentage of average girdle diameter. (Assignment 15)
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Per-carat price
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The price of a gem divided by its carat weight. (Assignment 20)
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Pick price
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A premium price for selecting stones from a parcel. (Assignment 20)
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Pinpoint (Pp)
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A very small included crystal that looks like a tiny dot at 10X. (Assignment 10)
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Pipe
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A deep vertical formation at the earth's surface that results from a kimberlite or lamproite emplacement. (Assignment 4)
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Pit (Pit)
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A small opening that looks like a tiny white dot at 10X. (Assignment 10)
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Planner
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The person who decides where to mark diamond rough for fashioning into the most profitable polished gem. (Assignment 9)
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Plot
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A map of a diamond's inclusions, blemishes, and facet arrangement. (Assignment 11)
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Point naif
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A seventeenth-century term for a diamond octahedron or other crystal shape on which the natural faces are apparent. (Assignment 9)
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Polish
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The overall condition of the facet surfaces of a finished diamond. (Assignment 8)
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Polish Lines (PL)
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Fine, parallel grooves and ridges left by polishing; can occur on any facet but do not cross facet junctions; transparent or white. (Assignment 10)
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Polish mark
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A feature that resembles an extra facet but lacks a distinct or straight facet junction. (Assignment 10)
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Polishing
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Placing and finishing facets on a rough diamond. Also called faceting. (Assignment 9)
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Potentials
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Diamonds that can be repolished to improve their clarity to an Internally Flawless grade. (Assignment 17)
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Primary crushing
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Reduction of newly mined ore to a manageable size. (Assignment 6)
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Primary deposit
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Gems found in the rock that carried them to the surface. (Assignment 5)
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Proportions
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The angles and relative measurements of a polished gem and the relationships between them. (Assignment 8)
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Recovery
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Any method used to separate diamonds from ore or alluvial sediments. (Assignment 6)
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Recutting
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Repairing damage or refashioning a polished diamond to improve its clarity, proportions, or color, or to modernize an old-style cut. (Assignment 17)
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Reflection
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The bouncing back of light when it strikes a surface. (Assignment 8)
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Refraction
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Change in speed and possible change in direction of light as it travels from one material to another. (Assignment 8)
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Refractive index (RI)
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A measure of the change in the speed and angle of light as it passes from one material to another. (Assignment 8)
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Relief
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Contrast between an inclusion and its host gem. (Assignment 11)
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Repolishing
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Refinishing a polished diamond to correct minor faults in its clarity or finish. (Assignment 17)
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Rhinestone
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A foilbacked, colorless, lead-glass diamond imitation. (Assignment 18)
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Rough Girdle (RG)
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Irregular, pitted, or granular surface of a bruted girdle. (Assignment 10)
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Sawing
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Dividing diamond rough into sections, either mechanically or by laser. (Assignment 9)
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Scaife
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A rapidly spinning horizontal disc coated with diamond powder, used to polish diamond rough. (Assignment 9)
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Scintillation
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The flashes of light and the contrasting dark areas you see when the diamond, the light, or the observer moves. (Assignment 8)
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Scoop
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A small shovel made of thin metal, used for picking up gems. (Assignment 20)
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Scratch (Scr)
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A thin, dull white line across the diamond’s surface; shows no apparent depth at 10X. (Assignment 10)
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Scrubber
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An apparatus that washes away dirt and clay from diamond-bearing ore. (Assignment 6)
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Secondary deposit
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Gems found away from their primary source. (Assignment 5)
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Selective absorption
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Process by which a material absorbs some wavelengths of light and transmits others. (Assignment 12)
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Separation
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Process of distinguishing natural minerals and gems from each other as well as from synthetics, simulants, and treated gems. (Assignment 18)
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Shape
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The face-up outline of a gem. (Assignment 16)
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Shape appeal
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A diamond's overall attractiveness in relation to others of the same shape and cutting style. (Assignment 16)
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Sharp
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A small diamond with a sharp edge, cemented into a dop and used to kerf another diamond in preparation for cleaving. Or, a small diamond used to brute diamonds or round up a girdle in the final stages of polishing. (Assignment 9)
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Sieve set
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Set of circular plates, each punched with precisely sized holes, used for sorting small, round gems by size. (Assignment 20)
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Sight
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Trading event where selected clients buy rough diamonds. (Assignment 2)
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Sightholder
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A diamond manufacturer or dealer invited by De Beers to buy rough diamonds. (Assignment 2)
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Single cut
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A simple diamond cut, with a table, eight crown facets, eight pavilion facets, and sometimes a culet. (Assignment 9)
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Single-channel marketing
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A direct, centrally controlled marketing route for rough diamonds. (Assignment 2)
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Singly refractive (isotropic)
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Possessing the same physical or optical properties in all crystal directions. (Assignment 7)
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Sorting pad
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A pad of white paper for sorting and showing gems. (Assignment 20)
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Special
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A rough diamond over 10.80 cts., sold separately to a sightholder who specializes in larger stones. (Assignment 2)
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Specific gravity (SG)
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Ratio of the weight of a material to that of an equal volume of water. (Assignment 7)
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Splitter
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A person who splits a rough diamond along a cleavage plane after it has been kerfed by a laser. Not to be confused with a cleaver, who is a master craftsman. (Assignment 9)
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Star length percentage
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The length of the star facets expressed as a percentage of the total distance between the girdle and the edge of the table facet. (Assignment 14)
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Step cut
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A cutting style with long, narrow, four-sided facets in rows parallel to the girdle on both the crown and pavilion. (Assignment 16)
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Subduction
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Process in which two crustal plates collide, forcing one under the other. (Assignment 4)
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Supplier of Choice
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Program adopted by De Beers in 2001, in which it required its sightholders to help increase market demand for diamonds. (Assignment 3)
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Supplier of Choice 2
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Program adopted by De Beers in 2007 to answer critics and resolve shortcomings of its original SOC program. (Assignment 3)
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Surface Graining (SG)
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Similar to internal graining, except it appears on the surface; results from irregularities in the crystal structure. (Assignment 10)
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Symmetry
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The exactness of a finished gem's shape and the placement of its facets. (Assignment 8)
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Synthetic diamond
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Manufactured diamond with essentially the same physical, chemical, and optical properties as natural diamond. (Assignment 19)
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Table gauge
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A transparent measuring device divided into millimeters and tenths of a millimeter, used to measure a diamond's table. (Assignment 14)
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Table percentage
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A diamond's table size expressed as a percentage of its average girdle diameter. (Assignment 14)
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Tang
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A device that holds the dop and allows polishers to adjust and maintain a diamond's angle during polishing. (Assignment 9)
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Tetrahedron
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In diamond, a group of five carbon atoms with one at the center. (Assignment 7)
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Thermal conductivity
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The relative ability of a material to transfer heat. (Assignment 7)
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Thermal expansion
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Capacity of a material to expand when it's heated. (Assignment 7)
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Thermal tester
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An instrument that measures thermal conductivity to help separate natural and synthetic diamonds from most simulants. (Assignment 18)
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Three-point diamond
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A diamond with its table nearly parallel to a possible octahedral face. (Assignment 9)
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Total depth percentage
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Table-to-culet depth, expressed as a percentage of average girdle diameter. (Assignment 14)
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Trace elements
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Atoms in a gem that aren't part of its essential chemical composition. (Assignment 7)
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Transmission
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The passage of light into or through a material. (Assignment 8)
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Twinned crystal
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Crystal distorted during growth, with two or more intergrown crystals with opposing crystal directions. (Assignment 7)
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Twinning Wisp (TW)
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A series of pinpoints, clouds, or crystals that forms in a diamond’s growth plane; associated with crystal distortion and twinning planes. (Assignment 10)
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Twisted stone
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A diamond with grain layers that are not on parallel planes, or one with partial twinning. (Assignment 9)
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Twisting
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A blocking technique in which the diamond is turned to position the softest polishing direction against the polishing wheel. (Assignment 9)
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Two-point diamond
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A diamond on which the table has been polished parallel to a dodecahedral plane. (Assignment 9)
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Unit cell
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Smallest group of atoms with the characteristic chemical composition and the basic crystal structure of a mineral. (Assignment 7)
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Vertical integration
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Involvement of a business or industry in all aspects of its product's market. (Assignment 3)
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Water
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A historic term once used in Europe to describe either the color or the transparency of a diamond. (Assignment 9)
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Wavelength
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The distance between two adjacent high points of an energy wave. (Assignment 8)
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Wholesaler
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Someone who sells to retailers rather than directly to consumers. (Assignment 1)
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X-ray separation
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A recovery method that uses X-rays to detect diamonds and an air jet to remove them from ore. (Assignment 6)
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On an emerald-cut diamond, very narrow corners should be noted underA.) Finish, a polishing detailB.) Finish, a symmetry variationC.) Proportions, as a shape-appeal factorD.) Proportions, as a length-to-width ratio variation
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C.) Proportions, as a shape appeal factor
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Where on a fancy-cut diamond might multiple facet reflections make it most difficult to detect clarity characteristics?
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Belly
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Calculate the length-to-width ratio of the following pear shape:Length - 7.51mmWidth - 5.19mm
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1.45:1
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Which of the following appears only on fancy cuts?A.) CutletB.) GirdleC.) Keel LineD.) Upper Girdle Facets
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C.) Keel Line
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On a marquise-shaped, brilliant cut diamond, pavilion angle variations can result inA.) A fisheyeB.) A bow-tieC.) Pavilion bulgeD.) Dark areas under the points
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B.) A bow-tie
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On emerald cuts, differences in the angles of the rows of pavilion facets causeA.) Wide cornersB.) Pavilion bulgeC.) A bow-tie effectD.) A shortened cutlet
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B.) Pavilion Bulge
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Compared to round brilliants, what is one difference in the color grading process for a fancy-cut diamond?
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Viewing Direction
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Princess cuts are popular in jewelry designs that call for A.) Curved linesB.) Pave settingsC.) An antique lookD.) Channel settings
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D.) Channel Settings
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What is the rounded end of a pear-shaped stone called?
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Wing
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Excessive pavilion bulge on emerald cuts results inA.) Excess weightB.) Increased beautyC.) Fewer setting problemsD.) Unattractive length-to-width ratio
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A.) Excess weight
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What are the slightly curved, central areas on the sides of some brilliant fancy-cuts called?
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Lobes
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How do you calculate the table percentage of a fancy cut diamond?
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Divide the width of the table by the width of the stone
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When you judge a diamond's shape appeal, you considerA.) Its bulge factorB.) Its total depth percentageC.) The symmetry of its corresponding partsD.) Whether or not its shape is graceful and pleasing
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D.) Whether or not its shape is graceful and pleasing
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What's considered under symmetry when grading a pear-shaped diamond?A.) Flat headB.) Bulging wingsC.) High shouldersD.) Cutlet placement
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D.) Cutlet placement
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What is a faceting style that replaces large bezel facets at the point of some diamonds with star and upper girdle facets called?
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French Tip
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The slightly curving center of a long side of a pear, marquise, heart, or oval.
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Belly
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A dark area across the center of an elongated brilliant cut.
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Bow-tie
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A cutting style in which triangular and kite-shaped facets radiate from a gem's center toward its girdle.
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Brilliant Cut
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The arrangement of a gem's facets
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Cutting style
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Any gemstone shape other than round
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Fancy cut
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A faceting style that replaces the large bezel facets at the points of marquises, pears, and hearts with star and upper girdle facets
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French tips
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A numerical expression of the relationship between the length and width of a fancy cut, where the value for the width is one.
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Length-to-width ratio
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A cutting style that combines step-cut and brilliant-cut facets
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Mixed cut
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Outward curve of the pavilion facets of a step-cut diamond
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Pavilion bulge
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The face-up outline of a gem
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Shape
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A diamond's overall attractiveness in relation to others of the same shape and cutting style
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Shape Appeal
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A cutting style with long, narrow, four sided facets in rows parallel to the girdle on both the crown and pavilion
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Step-cut
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Diamonds that can be repolished to improve their clarity to VVS1 or VVS2 grade
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Improvables
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Diamonds that can be repolished to improve their clarity to an internally flawless grade
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Potentials
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Repairing damage or refashioning a polished diamond to improve its clarity, proportions, or color, or to modernize an old-style cut
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Recutting
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Refinishing a polished diamond to correct minor faults in its clarity or finish
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Repolishing
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A mounting makes it impossible toA.) Appraise a diamondB.) Accurately weigh a diamondC.) Estimate a diamond's proportionsD.) Locate a diamond's clarity characteristics
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B.) Accurately weigh a diamond
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How do you see a diamond's clarity characteristics that might be hidden by prongs?
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Use reflections
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How do you color grade a mounted diamond?
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Hold its table beside the masterstone's table without letting the stones touch
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Accurate weight estimation of a mounted diamond requiresA.) A computer imaging systemB.) Very little skill or experienceC.) Careful measurements and a calculatorD.) Making adjustments for proportion variations
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D.) Making adjustments for proportion variations
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What requires the greatest adjustment to estimated weight?
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Thick Girdle
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What is the ultimate recutting consideration?
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The potential value of the finished diamond
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What is a diamond's recut style largely determined by?
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Its original cut
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Calculate the estimated weight of a round brilliant with the following dimensions:Average diameter - 7.25mmDepth - 5.45mmGirdle Thickness - Very Thick
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1.83ct.
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Calculate the estimated weight of a heart-shaped brilliant with the following dimensions:Length - 5.58mmWidth - 5.51mmDepth - 3.21mmGirdle Thickness - Medium
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0.58ct.
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What is the adjustment factor to use when estimating the weight of an emerald-cut diamond with the following dimensions?Length - 8.4mmWidth - 5.59mmDepth - 2.85mm
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0.0092
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What two factors do you need to find the crown height percentage?
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Crown angle & table percentage
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Which setting makes it most difficult to estimate a stone's weight?
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Bezel with a closed back
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Where does the chart of weight adjustment factors begin to apply?
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Slightly Thick
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A diamond grading system providesA.) Exact diamond market value to a buyerB.) A consistent way to communicate diamond qualityC.) Assurance to customers that they're getting the best pricesD.) Diamond descriptions that can change from country to country
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B.) A consistent way to communicate diamond quality
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Who is a wholesaler?
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Some who sells to retailers
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Diamond prices on wholesale price listsA.) Are not negotiableB.) Reflect a worldwide consensusC.) Are available free on the internetD.) Depend on the market conditions that exist when the lists are published
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D.) Depend on the market conditions that exist when the lists are published
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Large, high-quality diamonds areA.) sorted rather than gradedB.) Usually graded in their mountingsC.) Graded with a quick look under a loupeD.) Graded much more thoroughly than small, low-quality ones
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D.) Graded much more thoroughly than small, low-quality ones
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Diamond's supreme hardness and durability areA.) Due to diamond's rarityB.) A result of the conditions under which it formedC.) Surpassed by laboratory-grown diamond substitutesD.) A result of millions of years of battery by the forces of nature
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B.) A result of the conditions under which it formed
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Once diamond deposits are located, mining companiesA.) Begin extracting the diamondsB.) Recover the cost of exploration within the first yearC.) Are exempt from taxes and environmental regulationsD.) Must spend additional time and money to evaluate and develop them
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D.) Must spend additional time and money to evaluate and develop them
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What is an estimation of the value of an article?
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Appraisal
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What are the most consistent and dependable sources of diamond grades?
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Reputable gemological laboratories
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Substantial price discounts are available to retailers and jewelry manufacturers whoA.) Travel to diamond minesB.) Can buy in large quantitiesC.) Buy small quantities every monthD.) Always buy from the same supplier
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B.) Can buy in large quantities
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A diamond's clarity and color grades indicate itsA.) QualityB.) PopularityC.) Retail PriceD.) Wholesale Price
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A.) Quality
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Why don't reputable gemological laboratories grade mounted diamonds?
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Mountings hide details of clarity and cut
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How do dealers sort melee?
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Sieves
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Why has the diamond industry changed dramatically in recent years?
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The world's supply of diamond rough has increased
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The Argyle Mine in Australia contributed to A.) an economic slowdown in AustraliaB.) The rise of the cutting industry in IndiaC.) The decline of production in South AfricaD.) The rise of the cutting industry in Australia
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D.) The rise of the cutting industry in Australia
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Who are wholesale price lists organized?
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Specific combinations of the Four C's
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Who were the two major diamond producers before the discover of South Africa's diamond deposits?
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India and Brazil
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When did diamond sources start appear in South Africa?
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During the 1860s
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Who was the Central Selling Organisation?
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A rough diamond distribution agency
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What sparked the South African diamond rush?
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The Discovery of the Star of South Africa
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What is the soft, diamond-bearing material near the surface of a diamond field?
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Yellowground
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Who was Cecil Rhodes' main competitor in his early attempts to control diamond production?
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Ernest Oppenheimer
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Who established De Beers Consolidated Mines Ltd. in 1888?
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Cecil Rhodes
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What was De Beers Consolidated Mines Ltd. named after?
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The district where the Star of South Africa was found
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Who was the group that united in 1890 to buy and sell all of the output of the major diamond producers, including De Beers?
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London Diamond Syndicate
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What was Oppenheimer's answer to low diamond demand in the 1930s?
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Shut down operations at De Beers mines
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Why was the Diamond Information Center and the Diamond Promotion Service created?
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To Assist in diamond marketing efforts
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What the paths called that diamonds follow from mine to consumer?
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Diamond pipeline
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Sightholders purchase diamond rough byA.) Going directly to the minesB.) Attending invitation-only trading eventsC.) Selecting from lists sent out by De BeersD.) Contacting other sighthoders in their area
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B.) Attending invitation-only trading events
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What does De Beers require of its sightholders?
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Excellent reputation in the industry and the financial strength to make large purchase commitments
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What does the word "specials" refer to in the diamond trade?
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Diamond rough over 10.80cts.
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An agency designed to purchase, sort, evaluate, and sell rough diamonds
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Central Selling Organisation (CSO)
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An independent diamond prospector
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Digger
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A prospector's term for diamond deposits away from water
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Dry diggings
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A group of diamond merchants that united in 1890 to buy and sell rough diamonds
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London Diamond Syndicate
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The path diamonds followed from the mine to the consumer
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Diamond pipeline
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Trading event where selected clients buy diamonds
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Sight
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A diamond manufacturer or dealer invited by De Beers to buy rough diamonds
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Sightholder
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A direct, centrally controlled marketing route for rough diamonds
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Single-channel marketing
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A rough diamond over 10.80cts., sold separately to a sightholder who specializes in larger stones
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Special
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Which diamond mine's huge production influenced the world market in the late 1980s?
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Argyle
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What is the commitment to reserve a portion of the resources derived from any country for the economic development of that country called?
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Benefication
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What is a city, region, or country with a large number of gemstone manufacturers called?
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Cutting Center
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