Feature Gems & Gemology, Fall 1981, Vol. 17, No. 3

The Andradites of San Benito County, California

Discoveries in 1949 of andradite garnet in San Benito County, California, led to the formation in 1978 of a partnership to mine, cut, and market gem-quality andradite. These andradites are found in situ in serpentine outcrops and also in dry alluvial deposits. SEM microprobe analysis and X-ray powder diffraction show the chemistry and unit cell, respectively, to be nearly pure andradite. Cut stones and mineral specimens are produced in green, yellow, brown, and in combinations of these colors. Cut stones are generally under three carats and some are chatoyant. This is believed to be the only reported source of chatoyant garnet.