Benitoite (/bəˈniːtoʊaɪt/ titanium , found in hydrothermally. It forms in low temperature, high pressure environments typical of subduction. 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 discovered in 1907 by prospector James M. Couch in the San Benito Mountains roughly halfway between San Francisco. Couch originally believed the mineral was a corundum due to its resemblance of color. In 1909, a sample was sent to the University of California, Berkeley where mineralogist Dr. George D. Louderback realized it was a previously unknown mineral. Corundum (sapphire) has a defined Mohs hardness of 9, while benitoite is much softer. He named it benitoite for its occurrence near the headwaters of the San Benito River in San Benito County
Benitoite occurs in a number of isolated locations globally, but gemstone quality material has only been found in California at the Benito Gem Mine where it was first discovered. It has been correctly identified in Montana although they formed under slightly different conditions and only grow large enough to be considered an accessory mineral. In 1985 benitoite was named as the official state gem of California
Non-gem crystals of benitoite can have a very rare, six-pointed twinned form.