Benitoite Benitoite Benitoite on natrolite General Category Silicate mineral Chemical formula BaTiSi3O9 Identification Color Blue; Colorless Crystal habit Tabular dipyramidal crystals, granular Crystal system Hexagonal Cleavage [1011] Poor Fracture Conchoidal Mohs Scalehardness 6 - 6.5 Luster Vitreous Streak White Diaphaneity Transparent to translucent Specific gravity 3.6 Refractive index 1.757-1.759; 1.802-1.804 Pleochroism Dichroic (blue to white) Solubility Insoluble: HCl, H2SO4 Soluble: HF References [1][2] Benitoite is a rare blue barium titanium silicate mineral, found in hydrothermally alteredserpentinite. Benitoite fluoresces under short wave ultraviolet light, appearing light blue in color. It was first described in 1907 by George D. Louderback, who named it benitoite, “as it occurs near the head waters of the San Benito River in San Benito County,” California.[3][4] Uses of benitoite 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 usable material has limited this use. Associated minerals and locations 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 albite NaAlSi3O8 Blue Benitoite Crystals on white natrolite, Dallas Gem Mine, San Benito Co., California, USA Benitoite is a rare mineral found in very few locations including San Benito County, California,Japan and Arkansas. In the San Benito occurrence it is found in natrolite veins withinglaucophane schist within a serpentinite body. In Japan it occurs in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting a serpentinite body.[5] Benitoite is typically found with some combination of natrolite, joaquinite, and neptunite on a greenish-grey serpentinite base. Benitoite is the official state gem of California.