.Benitoite Mineral Facts:

Chemical Formula: BaTiSi₃O₉
Benitoite is a barium titanium silicate, found in veins in  altered serpentine. It 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. Initially identified by the first miners on site as sapphire, this mineral was formally described in 1907 by George D. Louderback, who gave it the name benitoite ater the location of its type occurrence near the headwaters of the San Benito River in San Benito County, California. Benitoite has been found at a number of sites the first discovery, but larger crystals and gemstone quality material has only been found at the Dallas Gem mine in California. It is California's official state gem.

Colors: Colorless to deep blue.
Localities other than the type location in California have produced tiny crystals with other colors including pink.

Hardness: 6.5

Density: 3.6

Cleavage: No cleavage. Conchoidal fracture.

Crystallography: Hexagonal
Crystals usually prismatic in habit or tapering hexagonal pyramids - an unusual crystal shape.

Luster:. Vitreous luster, transparent to translucent, with a high dispersion and refractive index.

Optics: (Refractive Index):  = 1.76

Composition, Structure and Associated Minerals:
The mineral is named After the type locality in San Benito County, California, USA. Benitoite typically occurs with an unusual grouping of associated minerals, along with minerals that make up its host rock. These associated minerals include: neptunite, natrolite, joaquinite, serpentine and albite.

Benitoite is a rare mineral found in very few locations across the world. known localities include San Benito and Santa Cruz Counties in California, as well as Japan and Arkansas. In the San Benito occurrence, it is found in natrolite veins within a glaucophane schist interlayered with a serpentine body. The Benitoite or Dallas Gem mine, located at the head waters of the San Benito river, is the type locality. In Japan, the mineral occurs in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting a body of serpentinite. In 1985 benitoite was approved by the legislature as the official state gem of California. The crystals are formed in fractures of a serpentine rock and deposited from hydrothermal solutions. These hot solutions contained a number of unusual elements dissolved within them, including barium, titanium, fluorine, iron, cesium, niobium, manganese and lithium in relatively high concentrations. The causes of such a solution and what other conditions caused the crystallization of these rare minerals is still not well understood.

Identification and Diagnostics
The mineral forms in characteristic trigonal (triangular) looking crystals. Nearly all specimens of  benitoite will also fluoresce a blue color under Ultraviolet light. It is normally identified by its unusual crystal habit, fluorescence, color, and mineral associations.

Occurrence, Localities and Origins:
Attractive specimens are very popular with mineral collectors, and transparent crystals are used as a gem stone. The sizes are mostly small, and benitoite gems over one carat are rare, and only a very few over 5 carats exist. The sapphire blue colored benitoite is a very valuable gem, ranging at times to around $1000 per a carat in clean, bright larger stones. Some small pink crystals have been found in Santa Cruz county in California.

 The attractive clusters of blue benitoite and black neptunite associated with a crust of white natrolite produce a truly desirable mineral combination that is a must have for all serious mineral collectors. The white natrolite covers over the crystals in most specimens, but is soluble in acids, and so most specimens have been treated with acid to better expose the beautiful benitoite and neptunite crystals. At the time of this writing, the old Dallas Gem mine site has been made open to collectors to work the dumps of previous operations for a fee. Some nice specimens have been collected in recent years, but the price to hunt is not cheap.

For information on gem Benitoite, see:  Benitoite - The California Gem

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