Diamond & Diamond Grading Exam 2024;everything you need to pass is here

Diamond & Diamond Grading Exam

2023;everything you need to pass is

here

Abrasion (Abr) - A series of minute nicks along the facet junctions of a

fashioned

diamond; gives the edges a white or fuzzy appearance. (Assignment

10)

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

girdle measurements of a round brilliant and dividing by two. (Assignment 14)

Bast - Frosted rough diamond. "Bark" in Dutch. (Assignment 9)

Bearded Girdle (BG) - Very small feathers that extend from the girdle surface into the

stone; can result from the cutting process. (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 Marks (Brn) - Hazy surface areas that result from excessive heat or from

uneven polishing caused by structural irregularities; also called polish marks or burned

facets. (Assignment 10)

Cavity (Cv) - An angular opening created when part of a feather breaks

away.

(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 color of a fancy-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 (Cl) - Large, severe, straight break along a plane of atomic

weakness;

considered an inclusion. (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)

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)

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Abrasion (Abr)

A series of minute nicks along the facet junctions of a fashioned diamond; gives the

edges a white or fuzzy appearance. (Assignment 10)

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 girdle measurements of a

round brilliant and dividing by two. (Assignment 14)

Bast

Frosted rough diamond. "Bark" in Dutch. (Assignment 9)

Bearded Girdle (BG)

Very small feathers that extend from the girdle surface into the stone; can result from

the cutting process. (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 Marks (Brn)

Hazy surface areas that result from excessive heat or from uneven polishing caused

by structural irregularities; also called polish marks or burned facets. (Assignment 10)

Cavity (Cv)

An angular opening created when part of a feather breaks away. (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 color of a fancy-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 (Cl)

Large, severe, straight break along a plane of atomic weakness; considered an

inclusion. (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)

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)

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)

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 Channels

Angular openings that start at the surface of the diamond and extend into it, often with

striations perpendicular to their length; considered inclusions. (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 round. (Assignment 16)

Fancy-colored diamonds

Diamonds that exhibit yellow or brown color beyond the Z range, or that exhibit any

other color. (Assignment 12)

Feather

A trade term for any break in a diamond. (Assignment 10)

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 surfacereaching 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 girdle 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 (GrCnt)

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

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 (IndN)

A portion of the rough's original surface, or skin, that dips below the polished

diamond's surface, or an opening left when a surface-reaching crystal drops out or is

forced out during polishing. (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 (IntGr)

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; not plotted. (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

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 girdle facet percentage

The length of the lower girdle 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)

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 (Nk)

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 and light brown, 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 diamondbearing 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)

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. (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)

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 girdle surface. (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 (S)

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