Abrasion:
Tiny nicks along facet junctions, producing white fuzzy lines instead of sharp crisp facet edges.

Baguette:
A step cut in the shape of a small rectangular stone which may be tapered at one end.

Bearded girdle or Bearding:
Tiny, numerous, hair like fractures extending into the stone.

Bezel:
A facet on the Crown, or upper part of the Diamond above the Girdle.

Blemish:
Surface imperfection external to the Diamond.

Bort:
Industrial grade diamonds

Bow-Tie Effect:
An effect caused by a shadowy area visible in some fancy shapes, caused by light leaking out the bottom of the Diamond.

Bruise:
An inclusions consisting of surface crumbling, often accompanied by tiny, root like feathers.

Burned Facet:
This facet may appear whitish, or burnt, as a result of the cutter polishing the facet "against the grain".

Carat Weight:
The metric carat, which equals 0.200 gram, is the standard unit of weight for diamonds and most other gems. If other factors are equal, the more a stone weighs, the more valuable it will be.

Cavity:
An inclusion consisting of a large or deep opening in the stone.

Chip:
A tiny piece missing caused by normal wear and tear, or by cutting.

Clarity:
A stone's relative position on a flawless to imperfect scale. Clarity characteristics are classified as inclusions (internal) or blemishes (external). The size, number, position, nature, and color or relief of characteristics determines the clarity grade. Very few diamonds are flawless, that is, show no inclusions or blemishes when examined by a skilled grader under 10X magnification. If other factors are equal, flawless stones are most valuable.

Cloud:
A group of tiny white inclusions which result in a milky or cloudy appearance.

Coated Diamond:
A diamond colored by a surface coating which masks the true body-color; the coating may be extensive (entire pavilion, for example), but is more often limited to one or two pavilion facets or a spot on the girdle.

Color:
Grading color in the normal range involves deciding how closely a stone's body color approaches colorlessness. Most diamonds have at least a trace of yellow or brown body color. With the exception of some natural fancy colors, such as blue, pink, purple, or red, the colorless grade is the most valuable.

Crown:
The upper part of the diamond above the girdle. It consists of a large flat area on top called a table, and several facets below it.

Culet:
The smallest facet at the bottom of the diamond.

Cut:
The proportions and finish of a polished diamond (also called make). Cut can also mean shape, as in emerald cut or marquise cut. Proportions are the size and angle relationships between the facets and different parts of the stone. Finish includes polish and details of facet shape and placement. Cut affects both the weight yield from rough and the optical efficiency of the polished stone; the more successful the cutter is in balancing these considerations, the more valuable the stone will be.

Emerald cut:
A step cut, usually rectangular.

Extra Facet:
A facet placed without regard for symmetry and not required by the cutting style.

Facet:
Plane, polished surface of a diamond.

Faceted Girdle:
Sometimes cutters polish the girdle into 32 or more facets.

Fancy Diamond:
A diamond with an attractive natural body color other than light yellow or light brown.

Feather:
A separation or break due to either cleavage or fracture, often white and feathery in appearance.

Flaw:
An imperfection of a stone.

Fracture:
A crack on the Diamond's surface.

Girdle:
The outer edge or the widest part of the diamond forming a band around the stone.

Grain Center :
A small area of concentrated crystal structure distortion usually associated with pinpoints.

Hardness:
Mineral's resistance to scratching on a smooth surface. Mohs scale of relative hardness consists of 10 minerals, each scratching all those below it in scale and being scratched by all those above it.

Hue :
Pure, spectral (prismatic) color. Hues include gradations and mixtures of red, orange, yellow, green, blue, violet and purple.

Included Crystal :
A mineral crystal contained in a diamond.

Inclusion:
Imperfection internal to the Diamond.

Internal Graining:
Internal indications of irregular crystal growth. May appear milky, like faint lines or streaks, or may be colored or reflective.

Irradiated diamond:
A diamond which has been exposed to radiation.

Knot:
An included diamond crystal which reaches the surface of a polished diamond.

Laser Drill Hole:
A tiny tube made by a laser. The surface opening may resemble a pit, while the tube usually looks needle-like.

Loupe:
Magnifying glasses usually of 10X.

Melee:
Small Diamonds less than .20 carat.

Mohs scale:
The ten-point scale of mineral hardness, keyed arbitrarily to the minerals talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond.

Natural:
Part of the rough Diamond remaining on the Diamond, having survived the cutting process. This is usually the sign of a good cutter attempting to maximize the weight retention of the rough Diamond.

Needle:
A long, thin included crystal which looks like a tiny rod.

Nick:
A notch near the girdle or a facet edge.

Off-Make:
A poorly proportioned Diamond.

Old European Cut:
Early round cut similar to the Round Brilliant Cut, but carrying a very small table and heavy crown. Not as popular today because it does not return the same brilliance as the modern brilliant.

Pavilion:
The bottom part of the Diamond, below the girdle.

Pinpoints:
Miniscule spots internal to a Diamond. A cluster of pinpoints can form a cloud.

Pit:
A tiny opening, often looking like a white dot.

Point:
100th of a carat.

Polish Lines:
Tiny parallel lines left by polishing. Fine parallel ridges confined to a single facet, caused by crystal structure irregularities, or tiny parallel polished grooves produced by irregularities in the surface.

Polish Mark:
Surface clouding caused by excessive heat (also called burn mark, or burned facet), or uneven polished surface resulting from structural irregularities.

Rough Girdle:
A grainy or pitted girdle surface, often with nicks.

Round Brilliant cut:
The most common cut containing 58 facets. Also the most brilliant cut, in terms of most efficient use of light to increase brilliance and fire, hence the name.

Saturation:
A color's position on a neutral to vivid scale.

Scratch:
A linear indentation normally seen as a fine white line, curved or straight.

Spread stone:
A Diamond with a large table and a thin crown height.

Surface Graining:
Refers to surface indication of structural irregularities. May resemble faint facet junction lines, or cause a grooved or wavy surface, often cross facet junctions.

Tone:
A color's position on a colorless-to-black scale.

Treated Diamond:
A diamond with a body color induced by some form of artificial irradiation, often in conjunction with controlled heating (known as annealing).

Twinning Wisp:
A cloudy area produced by crystal structure distortion, usually associated with twinning planes.