Benitoite

Benitoite is the rare barium-titanium cyclosilicate that became California’s state gem in 1985. Its sapphire-blue triangular dipyramidal crystals from a single deposit in San Benito County are unmistakable, and the species is essentially restricted to that locality in gem grade.

Occurrence

The Benitoite Gem Mine (Dallas Gem Mine), San Benito County, California, is the only commercial source — a serpentinite-hosted hydrothermal occurrence with benitoite, neptunite, joaquinite and natrolite. The mine ceased production in 2005, making material increasingly scarce.

Identification

Sapphire-blue triangular dipyramids + brilliant blue-white SW UV fluorescence + association with neptunite (black) and natrolite (white) on serpentine matrix. Distinguish from sapphire (corundum) by hexagonal habit and softness.

Collector Notes

Premier American collector gem; supply has dwindled since the mine closure. Faceted gem benitoite has the highest fire (dispersion) of any common gem species except diamond.