18 Photos
Benitoite
Chemical Formula	BaTiSi3O9
Species	Silicates
Crystal System	Hexagonal
Mohs Scale	6
Specific Gravity	3.6
Color	Blue, colorless
Streak	White
Luster	Vitreous
Refractive Index	n = 1.756 - 1.757 n = 1.802 - 1.804
Diaphaneity	Transparent, Translucent
Cleavage	Poor/IndistinctPoor on
Fracture	Conchoidal
Crystal Habit：Tabular dipyramidal crystals, granular

Benitoite (ben-EE-toe-ite) is a rare blue barium titanium silicate mineral, found in hydrothermally altered serpentinite. Benitoite fluoresces under short wave ultraviolet light, appearing bright blue to bluish white in color. The more rarely seen clear to white benitoite crystals fluoresce red under long-wave UV light.

It was first described in 1907 by George D. Louderback, who named it benitoite for its occurrence near the headwaters of the San Benito River in San Benito County, California.

Benitoite occurs in a number of sites, but gemstone quality material has only been found in California.^{[citation needed]} It is California's official state gem.

Associated minerals and locations

Benitoite typically occurs with an unusual set of minerals, along with minerals that make up its host rock. Frequently associated minerals include: natrolite, neptunite, joaquinite, serpentine and albite.

Benitoite is a rare mineral found in very few locations including San Benito County, California, Japan and Arkansas. In the San Benito occurrence, it is found in natrolite veins within glaucophane schist within a serpentinite body. In Japan, the mineral occurs in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting a serpentinite body.

In 1985 benitoite was named as the official state gem of California.