Benitoite, whose name derives from its type locality (San Benito County, California) is a blue silicate mineral, found in hydrothermally altered serpentinite. Benitoite fluoresces under ultraviolet light, appearing light blue in color.
Uses of benitoite
Benitoite's rarity makes it a minor ore for barium or titanium at best. Rather, benitoite's main uses are as collector's specimens, especially in specimens which show off this mineral's unique crystals, or specimens in which benitoite occurs with its commonly associated minerals. Benitoite's hardness also makes it suitable for use as a gemstone, though the general lack of useable material has limited this use.
Benitoite typically occurs with an unusual set of minerals, along with minerals that make up its host rock. Frequently associated minerals include:
natrolite Na2Al2Si3O10 · 2H2O
neptunite KNa2Li(Fe, Mn)2Ti2Si8O24
joaquinite NaBa2FeCe2(Ti, Nb)2(SiO3)8(OH, F) · 1H2O
serpentine (Mg, Fe)3Si2O5(OH)4
Notes for identification
Blue Benitoite Crystals on white natrolite, Dallas Gem Mine, San Benito Co., California, USABenitoite is a rare mineral, found in very few locations, most prominently in the Dallas Gem Mine in San Benito County, California, but also in Japan and Arkansas. Finding a blue mineral in these locations is a useful first step in identifying benitoite, but some key attributes should be kept in mind. First, benitoite's crystal habit is unusual, and would make a strong aid to identification. The associated minerals are also a key piece of information. Benitoite is typically found with some combination of natrolite, joaquinite, and neptunite on a greenish-grey serpentinite base. Finally, benitoite's fluorescence is used for identification purposes.