ROCK & GEM FIELD GUIDE: Oregon Sunstone

Sunstone is the transparent, gem-quality variety of the mineral labradorite, a calcium-rich feldspar in the plagioclase series.

- DR. STUART MILLS & PAM FREEMAN

It is one of the most popular U.S. gems and is notable for its warm colors and internal shiller (shimmer). Its specific shimmering effect is called aventurescence, uniquely caused by tiny copper platelets within the crystal. Unlike most feldspars, which are opaque or iridescent, Oregon sunstone is prized for its transparency, with the best Oregon sunstone gems having the most brilliant shimmer and saturation.

Formation