Glossary of Terms

Asterism

Effect exhibited on some polished cabochons that cause them to reflect a billowy, star-like formation of concentrated light which moves around when rotated. Asterism is caused by dense inclusions of tiny, parallel, slender, fibers in the mineral which cause the light to reflect in such an interesting manner. Gemstones that display asterism may exhibit four, six, and sometimes twelve rayed "stars", depending on the inclusions, size, and facet.