Benitoite is a rare blue barium titanium silicate mineral. It changes color under shortwave ultraviolet light from bright blue to bluish white. Under longwave ultraviolet light, the clear to white benitoite crystals fluoresce red. It was first described in 1907 by George D. Louderback.

He named it benitoite since it occurred near the head waters of San Benito river in San Benito County in California.

Benitoite occurs in a number of sites, but gemstone quality material has only been found in California. It was made California’s official state gem in 1985. Benitoite typically occurs with an unusual set of minerals, along with minerals that make up its host rock. Benitoite is a rare mineral found in very few locations including San Benito County, California, Japan and Arkansas.