History · Geology
About Benitoite Gem Mine
The Benitoite Gem Mine (Dallas Gem Mine) in San Benito County, California, is the world’s only commercial source of gem-quality benitoite — California’s state gem since 1985. The deposit was active 1907-2005 and remains the type-quality producer of sapphire-blue triangular benitoite crystals.
Geology
The deposit is a unique hydrothermal vein system in serpentinite of the Coast Ranges. Late-stage Ba-Ti-Si-rich fluids precipitated benitoite, neptunite, joaquinite and natrolite in a globally unique paragenesis.
Notable Minerals
Benitoite (sapphire-blue triangular dipyramidal crystals — the species archetype, fluoresces brilliant blue under SW UV), neptunite (jet-black tabular crystals — characteristic Benitoite Gem Mine companion), natrolite (white needle aggregates — host matrix), joaquinite, crossite, serpentine. The classic combination “benitoite + neptunite + natrolite” defines American mineralogical aesthetics.
Collector Notes
The mine ceased commercial operation in 2005; supply has tightened steadily since. Benitoite has the highest dispersion of any common gemstone except diamond, making faceted stones display extraordinary “fire.”
Minerals Produced Here
- Benitoite (蓝锥矿)
- Natrolite (钠沸石)
- Serpentine (蛇纹石)
