Gemstone Glossary

Radiant cut

Cut for octagonal stones similar to the emerald cut in outline but with a facet alignement similar to the brilliant cut, developed by the american diamond cutter Henry Grossbard.

Refractive index

Abbr. R.I., important feature in gemstone identification, the sine-relation of incident ray and refracted ray (refracted rays in doubly refractive materials).

Refractometer

Optical instrument for the measurement of the refractive index

Rose cut

Round, facetted stone without pavilion and 3 to 48 crown (upper part) facets