What is "benitoite"

n. (context mineral English) A rare hard blue silicate mineral found in hydrothermally altered serpentinite.

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

Benitiote has a rare 5 pointed crystal form, and an even rarer 6 pointed form, "star of David", with about 24 samples known.