Refers to a diamond that glows (fluoresces) strong blue under long wave ultraviolet light; in the past the term was used misleadingly to imply a diamond with superior colour. In fact, some diamonds with a high colour grade that have very strong fluorescence can look oily or milky under daylight.
Oval Cut
Diamond cut or shaped into an ellipse and covered with triangular facets in a brilliant cut style.
Old Mine Cut
Diamond cut or shaped in an old-style cushion cut manner, with a deep pavilion depth, closed table, high crown height, and large facet on the culet.
Off-Make
Octahedron
One of the most coveted crystal shapes for a rough diamond, with eight triangular faces that look as though two four-sided pyramids have joined together at the base.
Nick
Type of diamond blemish that that appears as a tiny break out of the edge of a diamond, not large enough to be a called a chip and usually confined to the girdle. Nicks affect the polish grade of a diamond.
Needle
Natural Diamond
Diamond mined from the earth, unlike a synthetic diamond, formed completely by nature without any human intervention or treatments.
Natural
Part of the original “skin” of a rough diamond that has been left on the polished diamond. Naturals affect the polish grade of a diamond, but do not have a significant impact if confined to the girdle area where they are usually located.
Nailhead
Unattractive black shadow under the center of a round brilliant cut diamond that has too deep of a pavilion. The shadow is caused by the reflection of the table. Diamonds with a nailhead look dark, lacking brilliance and life.