Refers to the surface lustre of diamond.

The word diamond comes from the ancient Greek word adamas (αδαμας), meaning unconquerable.

Africa dominated diamond production during the 20th century, with mining activity centred in Botswana and South Africa and concentrated in the hands of De Beers. But, although Africa is still the centre of the industry, the last decade has seen an expansion of production in Canada and Russia.

American Gem Society (AGS):
Originally created to be an educational institution for gemological studies to develop and promote universally-accepted standards for grading cut, AGS now provides independent certification reports on Ideal diamonds.

Appraise, Appraisal:
Appraisal is carried out on rough and polished diamonds at many stages to assess quality and market values.

Arrows, Hearts and:
An optical pattern discernable in some well-proportioned diamonds, and marketed as a demonstration of excellent cutting.

A rectangular or oblong step or "trap" cut used for diamonds and other gemstones.

A color description used for certain fancy brownish yellow diamonds.

Best Practice Principles:
An "Assurance Program" of the De Beers diamond group, as well as to Sightholders and their business partners "to enhance and uphold the fine values diamonds represent".

An impurity that occurs on the surface of a diamond, either in nature or during the mining process.

Body Color:
The color of light seen through a diamond without any dispersion, usually viewed through the side of a stone. A diamond's actual color.

Bow Tie:
An optical effect adversely affecting marquise and other fancy cuts of diamonds, can be minimized by careful cutting using best proportions and angles.

The brightness that comes from the center of a diamond. Brilliance is created when light enters through the top of the diamond (its "table"), travels to the bottom facets (pavilion facets), and is then bounced back out through the table, where the light is most visible to the naked eye.

Brilliant Cut:
One of three styles of faceting arrangements, its faceting is designed to maximize brilliance. Round diamonds, ovals, radiants, princesses, hearts, marquises, and pears are brilliant cuts.

The unit of weight by which a diamond is measured: One carat equals 200 milligrams.

Carbon Spots:
The term refers to crystals within a diamond that have a dark appearance, rather than a white or transparent appearance, when viewed under a microscope. In most cases, these are not visible to the naked eye, and do not affect a diamond's brilliance.

A hole or void in a diamond or other gemstone, either internal or extending to the surface. Internal cavities may naturally contain gas, liquid, solid, a combination of two or three of these, and there may be phase changes depending on ambient temperature

A diamond which has been graded and certified or certificated by a gemological laboratory.

Certificates, Certification:
Documents issued by gem labs attesting the genuineness and stating the quality of a diamond or other gemstone.

Channel Setting:
A setting style or method where there is no metal showing between stones.

Relates to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects called blemishes. Clarity is one of the Four Cs of diamond grading, the others being carat, color, and cut.

A word used informally to mean flawless, or at least to infer flawlessness.

One of the two methods used by diamond cutters to split rough diamond crystals in the diamond cutting process.

Some low clarity diamonds with significant cloudy or milky areas.

Closed Culet:
A culet which consists of a point rather than a facet.

Color Grading:
A grading system based on diamonds' colorlessness (for white diamonds) or their spectral hue, depth of color and purity of color (for fancy color diamonds). For white diamonds, GIA and AGS use a grading system which runs from D (totally colorless) to Z (light yellow).

What most people describe as white, regarded as being the best "color.".

The upper portion of a diamond, which lies above the "girdle."

Crown angle:
The angle of the facets that surround the table which creates "dispersion," or fire, in a diamond.

Crown Height: 
The height or depth of the top part of a diamond, above the girdle.

A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged.

A shape of diamond, four sided with curved sides.

This refers both to the proportions and finish of a polished diamond. As one of "the Four Cs" of diamond value - the others being carat, color, and clarity - it is the only man-made contribution to a diamond's beauty and value.

De Beers: 
Dominant diamond mining and marketing company since the nineteenth century. Creators of the slogan "A diamond is forever."

The height of a diamond from the culet to the table. The depth is measured in millimeters.

A crystal made up of 99.95% pure carbon atoms arranged in an isometric, or cubic, crystal arrangement.

Diamond Cutting:
The method by which a natural, rough diamond is shaped into a finished, faceted stone.

Diamond Gauge:
An instrument that is used to measure a diamond's length, width and depth in millimeters.

The appearance of small flashes of color across the surface of the diamond as it is tilted; also called a diamond's "fire."

EGL, European Gemological Laboratory: 
European Gemological Laboratory claims to be an international independent leader in diamond grading and training for all diamond business solutions.

Eight Cut: 
Also called "single cut," diamonds, usually small diamonds with only 18 facets instead of the full 58 on a brilliant cut.

Emerald Cut:
A square or rectangular-shaped diamond with cut corners.

A term describing a diamond with no blemishes or inclusions visible to the naked eye; at least SI in clarity.

Face Up: 
Refers to the viewing angle of a polished diamond, so that the table faces approximately towards the viewer, rather than the viewer looking through the side of the stone.

The smooth, flat faces on the surface of a diamond. A round brilliant has 58 facets (or 57 if there is no culet).

Fancy Color: 
Most diamonds are near-colorless, but strongly colored diamonds (pinks, yellows, etc.) are rare and valuable, and are usually known as "fancies".

Fancy Shape:
Any diamond shape other than round.

These are small fractures in a diamond, usually caused by the tremendous stress that the diamond suffered while it was growing underground.

A term covering every aspect of a diamond's appearance that is not a result of the diamond's inherent nature when it comes out of the ground.

See "dispersion."

A detrimental optical effect in the center of a diamond (resembling a black hole) which is cut too shallow, or with an overlarge table.

In inclusion or other feature which is visible or reduces clarity in diamonds or other gems.

Without any inclusions or features adversely affecting clarity.

An effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light.

Four Cs: 
Cut, color, clarity, and carat weight. The four well-known factors affecting the price of a diamond.

Full Cut: 
With 58 facets, i.e. usually a brilliant cut, and usually round.

Gemological Institute of America (GIA):
Founded in 1931, a non- profit organization upholding the highest standards for grading diamonds and other precious gems.

A person with expertise and formal qualifications in gemology.

The outer edge, or outline, of the diamond's shape, described by its appearance at its thinnest and thickest points (extremely thin; thin; medium; slightly thick; thick;
extremely thick).

Girdle Facet:
Any of the facets adjacent to the girdle on a brilliant cut or other diamond, split into upper (crown) girdle facets, and lower (pavilion) girdle facets.

A recognized measure of an aspect of quality, mainly clarity and color, but can also be applied to proportion and other aspects.

Heart-shape Cut:
A type of fancy diamond cut, resembling the popular Valentine's Day shape.

Hearts and Arrows: 
An optical pattern discernable in some well-proportioned diamonds, and marketed as a demonstration of excellent cutting. Usually found in well cut Ideal diamonds.

I1, I2, I3, Included, Imperfect:
I1, I2, and I3 are all grades in the GIA clarity scale.

Ideal, Ideal Cut:
Theoretically perfect cutting proportions for (round brilliant cut) diamonds. Exact specifications vary.

I.G.I., International Gem Laboratory:
Organization with laboratories located in the heart of the gem & jewelry districts throughout the world, including New York, Antwerp, Mumbai, Bangkok and Tokyo.

Possessing inclusions, mainly internal features which impair the brilliance or clarity of a diamond.

A clarity characteristic found within a diamond. Most inclusions were created when the gem first formed in the earth. Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy.

Internally Flawless, IF:
A clarity grade which allows for no naturals or other surface features or imperfections.

Kimberley Process:
An international agreement on methods to counter conflict diamonds.

The yellow or blue "ground" rock which forms diamond "pipes", and in which most diamond rough is found.

Length-to-width ratio:
A comparison of how much longer a diamond is than it is wide, used to analyze the outline of fancy shapes only.

French word for magnifying glass, universally applied to the version used by most jewelry professionals, with a 10X magnification, although other powers are used.

Loupe Clean:
Indicating that a diamond contains no visible inclusions when using the industry standard magnification of ten times (10x).

Lower Girdle Facet:
A diamond facet adjacent to and below the girdle (on the pavilion).

Some diamonds luminesce (emit light) when exposed to sunlight or other ultraviolet-light sources. The light the diamonds emit is usually light blue, but yellow, orange, and red luminescence occurs in some stones.

The luster of a diamond is its highly reflective surface sheen due to its high refractive index combined with the highly polished surfaces.

A 'made' stone is one of excellent proportion and finish.

Main Facets:
The first sixteen facets to be ground onto rough diamonds, apart from the table and culet, also the main pavilion facets (the first eight on the pavilion).

Some over-fluorescent diamonds have a cloudy or milky appearance, especially in ultra-violet light or daylight.

Marquise Cut:
A fancy shape diamond which is elongated with points at each end.

Modified Brilliant Cut:
A diamond cut in a shape or style other than round, such as oval, pear, marquise, heart, princess, radiant, or trilliant. Could also be applied to round stones based on the brilliant cut.

Small parts of the original rough diamond's surface which are left on the polished diamond, frequently on or near the girdle.

Oval Cut:
A fancy shape diamond which is an elongated version of a round cut.

From French, literally paved. Diamonds are other gemstones set in such a way that they substantially cover a surface of a piece of jewelry.

The lower portion of the diamond, below the girdle.

Pavilion Angle:
The angle between the main pavilion facets and the girdle. In diamond cutting and proportion, this is the single most important dimension, and should be around 40.75° to 41°.

Pavilion Facet:
Any of the facets on the pavilion of a diamond, but usually referring to the main pavilion facets, as distinct from the lower girdle facets.

Pear Cut:
A fancy shape diamond that resembles a teardrop.

From French "prick", a needle or other inclusion in a diamond. First piqué (P1) is a clarity grade, the American equivalent is I1.

A unit of measurement used to describe the weight of diamonds. One point is one-hundredth of a carat.

Refers to any blemishes on the surface of the diamond which are not significant enough to affect the clarity grade of the diamond. Regarded as an indicator of the quality of as diamond's cut, it is graded as Ideal, Excellent, Very Good, Good, Fair or Poor.

Princess Cut:
A brilliant cut fancy shape that can be either square or rectangular.

The consideration of the overall shape of a diamond taking each part in relation to all other parts.

Another word for clarity.

Radiant Cut:
A brilliant cut fancy shape that resembles a square or rectangle with the corners cut off.

A comparison of how much longer a diamond is than it is wide.

Important optical effect, whereby light bounces off a surface.

Important optical effect, the deviation of light when it passes from one medium to another, e.g. air to diamond.

Rough is the word used to describe all uncut or unpolished diamonds.

A jewelry setting with an empty set of prongs for mounting a diamond center stone that the customer selects separately.

A word often used interchangeably with "cut", although the two have different meanings. Shape should refer to the basic outline type, such as round, oval, square, princess, radiant, cushion, oblong, emerald, baguette, pear.

An individual or company which attends De Beers diamond selling meetings, known as sights.

A very small round diamond with only 16 or 17 facets, instead of the normal 57 or 58 facets of a full cut round brilliant.

Star Facet:
One of the eight facets adjacent to the table on a brilliant cut diamond, so called because they from an eight pointed star when viewed from above.

Step Cut:
One of three styles of faceting arrangements, with broad, flat planes resembling stair steps).

Refers to variations in a diamond's symmetry, regarded as an indicator of the quality of as diamond's cut; it is graded as either Ideal, Excellent, Very Good, Good, Fair or Poor.

The flat facet on the top of the diamond. It is the largest facet on a cut diamond.

Table percentage:
The value which represents how the diameter of the table facet compares to the diameter of the entire diamond.

Trap Cut:
Also known as step cut. A traditional way to cut rectangular, octagonal or other non - round diamonds, including emerald cuts.

Trilliant Cut:
A type of brilliant fancy shape that is triangular.

Upper Girdle Facet:
Any of the sixteen facets on the crown (top), adjoining the girdle of a diamond.

Used on color grading of fancy colored diamonds to denote the most intensely colored stones, not the darkest.