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Benitoite
Archivo:Benitoite new.jpg
Benitoite on natrolite
General
Category Mineral
Chemical formula Plantilla:BariumPlantilla:TitaniumSi3O9
(barium titanium silicate)
Identification
Color Blue; Colorless
Crystal habit Tabular dipyramidal crystals, granular
Crystal system Hexagonal
Cleavage [1011] Poor
Fracture Conchoidal
Mohs scale hardness 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][3]

Benitoite is a rare blue silicate mineral, found in hydrothermally altered serpentinite. Benitoite fluoresces under short wave ultraviolet light, appearing light blue in color. Dr. Louderback, who conducted the discovery examination of this mineral, named it Benitoite, “as it occurs near the head waters of the San Benito River in San Benito County,” California.[4][5]

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 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 Plantilla:SodiumPlantilla:AluminumSi3O10Plantilla:Hydrate
neptunite Plantilla:PotassiumPlantilla:SodiumPlantilla:Lithium(Fe, Plantilla:Manganese)2Plantilla:TitaniumSi8O24
joaquinite Plantilla:SodiumPlantilla:BariumFePlantilla:Cerium(Plantilla:Titanium, Plantilla:Niobium)2(SiO3)8(OH, Plantilla:Fluorine)Plantilla:Hydrate
serpentine (Mg, Fe)3Si2O5(OH)4
albite Plantilla:SodiumPlantilla:AluminumSi3O8
Archivo:Benitoite09.jpg

Blue Benitoite Crystals on white natrolite, Dallas Gem Mine, San Benito Co., California, USA

Benitoite is a rare mineral, found in very few locations, most prominently in southern San Benito County, California, but also in Japan and Arkansas. In the San Benito occurrence it is found in natrolite veins within glaucophane schist within a serpentinite body. In Japan it occurs in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting a serpentinite body.[6] 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.

Trivia[]

Benitoite is the official state gem of California.[7]

Benitoite is the official gem of E Clampus Vitus.

References[]

  1. http://webmineral.com/data/Benitoite.shtml WebMineral Listing
  2. http://www.mindat.org/min-624.html MinDat Listing
  3. http://mineral.galleries.com/minerals/silicate/benitoit/benitoit.htm Mineral Galleries
  4. Louderback, George Davis. Bentiote, A New California Gen Mineral. Bulletin of The Department of Geology, Vol. 5, No. 9. University of California Publications. July, 1907
  5. http://www.mineralsocal.org/scfm/newsletters/2002%20march.htm Friends of Mineralogy review of benitoite
  6. http://rruff.geo.arizona.edu/doclib/hom/benitoite.pdf Handbook of Mineralogy
  7. http://www.consrv.ca.gov/cgs/geologic_resources/mineral_resource_mapping/ Mineral Resources California Geologic Survey. Accessed December 31, 2005

fr:Benitoïte it:Benitoite lt:Benitoitas nl:Benitoiet pl:Benitoit pt:Benitoíte fi:Benitoiitti

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