DIAMOND TERMINOLOGY AND SPECIFICS
Any surface imperfection on a fashioned diamond. Also, a natural or an extra facet, visible on or through the crown, usually is considered a blemish.
The intensity of the internal and external reflections of white light to the eye from a diamond or other gem in the face-up position.
Any transparent inclusion in a diamond; e.g., a tiny diamond crystal or a grain of a different mineral.
A unit of weight for diamonds and other gems. The carat formerly varied somewhat in different countries, but the metric carat of .200 grams, or 200 milligrams, was adopted in the United States in 1913 and is now standardized in the principal countries of the world. There are 100 points in a carat.
An inclusion in a diamond that appears black to the unaided eye.
(a) A curved break on a diamond that extends from a surface edge. (b) A small rose-cut diamond or single-cut melee. (c) A cleavage piece of diamond that weighs less than one carat. (d) A small, irregularly shaped diamond.
The relative position of a diamond on a flawless-to-imperfect scale.
A culet on a diamond that is too small to be resolved with the unaided eye and that can be seen only with difficulty under 10x. The term is rarely used to refer to a pavilion point or ridge with no "culet."
A term used by some diamond men to designate a small table diameter. However, its interpretation and use varies. It may refer to a diameter less than the American cut 53% (of the girdle diameter) or, more frequently, to a table smaller than about 60%, because so many of the stones cut today have tables well over that figure.
A group of tiny white inclusions, composed of minute hollow spaces, or very small patches of tiny crystals or other impurities that produce a cottony or clouded appearance in a n otherwise highly transparent diamond. A cloud may be so minute that it is difficult to see under 10X, or it may be large enough to deprive the entire stone of brilliancy.
That part of any fashioned gemstone above the girdle.
The small facet that is polished parallel to the girdle plane across what would otherwise be the sharp point or ridge that terminates the pavilion of a diamond or other gemstone. Its function is to reduce the possibility of damage to the stone.
A certificate awarded to those who complete successfully the "Diamond Course" of the Gemological Institute of America, which requires passing the diamond-grading and diamond-appraising instruction and practice.
The durability of a gem depends both on its hardness and "toughness." It may be quite tough but easily scratched, or it may be exceedingly hard but lack toughness because of easy cleavage. Diamond is highest on the scale of hardness and, despite it rather easily developed octahedral cleavage, it is among the toughest of gemstones.
(a) A term used in brillianteering for the entire group of facets that can be placed won a diamond without reposition it in the dop; vis., two star facets and four upper-break facets or four lower-break facets. (b) In crystallography, a natural, plane surface on a crystal.
A plane, polished surface on a diamond or other gemstone.
The operation of placing facets on a diamond or other gem.
When the plane of cleavage or fracture in a diamond is viewed at right angle to it, the appearance is often reminiscent of a feather. Thus, cleavage and fractures are often called "feathers."
The resistance of a substance to being scratched.
A minor chip out of the surface of a fashioned diamond, usually caused by a light blow.
In weighing diamonds, one-hundredth part of a carat, each hundredth being called a point; e.g., 32 hundredths (.32) of a carat is said to be a 32-point diamond, or a thirty-two pointer. 100 points = 1 carat, 141+ carats = 1 ounce, and about 2268 carats = 1 pound.
The relative smoothness of a surface, or the degree to which the finish of the surface approaches optical perfection. A well-polished diamond shows no wheel marks or burn marks under 10X.
Narrow, shallow, elongated, rough-edged depressions on the surface of a fashioned diamond, usually appearing as faint white lines under magnification.
The exactness of placement and shaping of opposed facets and other portions of a diamond. Symmetry is judged on the basis of the degree to which these opposed features yield exact mirror images.
The large facet that caps the crown of a faceted gemstone. In the standard round brilliant, it is octagonal in shape and is bounded by eight star facets.
The size of the table of a fashioned diamond, expressed as a percentage of the stone's narrow-girdle diameter, is a dimension used in proportion analysis. On a round brilliant, it is measured from corner to opposite corner, rather than from flat side to flat side.
DIAMOND CENTER AND SIDE STONE SHAPES
A French word meaning "rod." A style of "step cutting" for small, rectangular or trapeze-shaped gemstones, principally diamonds
It is called a brilliant cut because it is designed to maximize brilliance. Round diamonds, ovals, radiants, princesses, hearts, marquises, and pears all fall within this category of cut.
The older form of the brilliant cut, having a girdle outline approaching a square with rounded corners. Essentially an old-mine cut.
A square or rectangular-shaped diamond with cut corners. On the crown, there are three concentric rows of facets arranged around the table and, on the pavilion, there are three concentric rows arranged around the culet. This type of cut is also known as a Step Cut because its broad, flat planes resemble stair steps.
Any style of diamond cutting other than the round brilliant or single cut. Fancy cuts include the marquise, emerald cut, heart shape, pear shape, keystone, half moon, kite, triangle, and many others. Also called the "fancy-shaped" diamond or "modern cut."
A type of fancy diamond cut, which is cut to resemble the popular Valentine's Day shape.
A type of fancy shape diamond which is elongated with points at each end.
A brilliant style of cutting in which the girdle outline is elliptical; i.e., a rounded oblong. Also called the "oval brilliant cut".
A type of fancy shape diamond that resembles a teardrop.
A type of brilliant cut fancy shape that can be either square or rectangular.
A type of brilliant cut fancy shape that resembles a square or rectangle with the corners cut off.
A term used to refer to a ring containing a single diamond or other gem.
A type of brilliant fancy shape that is triangular. Popular for side stones.
SPECIAL DIAMONDS
When a diamond is dark gray, a very dark green or truly black, it is referred to in the trade as a "black diamond." Such a stone may be opaque to nearly semitransparent.
A diamond with a distinctly blue body colour, even thought very light in tone, is a fancy diamond. Diamond that are blue in both daylight and incandescent light are rare, although fluorescence stones that show a blue colour in daylight are comparatively common. A blue colour may also be induced artificially.
An intensely coloured "yellow" diamond. The yellow may be very slightly greenish or slightly orangey, but it must be deep enough to be a distinct asset. Such a diamond is called a fancy.
Any diamond with a natural body colour strong enough to be attractive, rather than off colour. Reddish (the pure red of ruby is extremely rare), blue and green are very rare; orange and violet, rare; strong yellow, yellowish-green brown and black stones are more common.
A term often used loosely in the trade to describe any diamond of pale reddish, purplish-red, purplish or violetish hue. Diamonds of colours other than pale reddish are sometimes described as rose pink, rose coloured, peach blossom, heliotrope and similar terms. Such a diamond is called a "fancy."
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