Optical Effects of Phenomenal Cabochons
Learn how the structure, inclusions and properties of some gemstones interact with light to create unusual visual effects.
Prasiolite with Inclusion Influenced by Brazil-Law Twinning
A prasiolite specimen displaying Brazil-law twinning, usually seen in the amethyst variety of quartz, is examined.
Spring 1991 G&G Lab Notes
This section, from the Spring 1991 issue of Gems & Gemmology, is a compilation of interesting finds from GIA’s laboratories.