Benitoite is an attractive blue mineral, named for San Benito Co. in California (USA), where the type locality is located. The type locality has changed name several times but is usually referred to simply as 'Gem Mine' or by the older name 'Dallas Gem Mine'. Benitoite has a complex crystal structure and is the only mineral in its space group. It is vividly fluorescent, and even intergrown crystals are in high demand from collectors of fluorescent minerals. Attractive Benitoite crystals are etched out of Natrolite veins in a fine-grained amphibolite, that may also carry superb lustrous crystals of Neptunite. Benitoite is the state mineral of California, and is a highly priced gem when clean. In the late 1990s a new, heat-treated salmon-coloured 'Imperial Benitoite' came on the gem market. Benitoite only occurs in a few localities such as 'Minera Numero Uno' near the Gem Mine and also intergrown with barium silicates in the Clear Creek and Big Creek deposits (Fresno Co., California).