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332 Cards in this Set

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