- The display of reflections from the polished facets of a gemstone seen by the observer when either the illuminant, the gemstone or the observer is in motion—a flashing or twinkling of light from the facets.
- Narrow, shallow, elongated, rough-edged depressions on the surface of a fashioned diamond, usually appearing as faint white lines under magnification.
- Single Cut
- A simple form of cutting that has a circular girdle, a table, eight bezel facets, eight pavilion facets and sometimes a culet. It is used mostly for small diamond melee.
- Slightly Imperfect
- A grade of relative imperfection in a diamond. It signifies a more flawed condition than very slightly imperfect but less than imperfect. In general, stones are called “slightly imperfect” only if the flaws they contain are not visible face up to the unaided eye of a trained observer.
- Slightly Yellow
- A diamond color grade that is used by some dealers for a stone showing an obvious yellow tint to the unaided eye.
- A term used to refer to a ring containing a single diamond or other gem.
- Spread Stone
- A term that is used frequently in the diamond trade to refer to a stone that has been cut with a large table and a thin crown, to retain greater weight from the two sawn pieces of an octahedron than is possible by using ideal proportions. In a strict sense, any increase in table diameter over the ideal 53% constitutes spreading; however, it is a general trade practice to apply the term only to those stones with tables that measure in excess of about 60%.
- Square Emerald Cut
- A form of step cutting with a square girdle outline but modified by corner facets.
- 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.