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Perfect Triangular Benitoite Crystal

The Mineral benitoite




Benitoite was first discovered in 1907, and upon its initial discovery was thought to be Sapphire. The crystal structure of Benitoite is unique, and is the only significant mineral in its crystal class. It crystallizes in a rare hexagonal sub-class called ditrigonal-dipyramidal.

Most Benitoite crystals were originally deeply embedded in thick Natrolite; specimens are prepared for collectors by dissolving the surrounding Natrolite in acid to expose the Benitoite crystals. The blue Benitoite on a white Natrolite matrix and usual association with black Neptunite makes a very aesthetic mineral specimen.

Benitoite is named after its locality in San Benito Co. in California, where this mineral was first found in a remote area far from civilization. This region is the only source of Benitoite, aside from some very sporadic and extremely limited occurrences worldwide.

For additional information, see the gemstone section on Benitoite.
Chemical Formula BaTiSi3O9
Composition Barium titanium silicate
Color Light blue to deep indigo blue. Also bluish-gray and purplish-blue. May be zoned with lighter and darker color regions and white zones.
Streak Colorless
Hardness 6 - 6.5
Crystal System Hexagonal
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates		 In well-formed, tabular crystals that are triangular in shape, often with slightly flattened points or sub-triangular points. Crystals may be in isolated crystals or interconnected. Twinning as stubby hexagonal prisms are also known, and a rare oddity is a perfectly aligned penetration twin shaped as a star of David.
Transparency Transparent to translucent. Inclusions can cause it to be opaque.
Specific Gravity 3.6
Luster Vitreous
Cleavage None
Fracture Uneven
Tenacity Brittle
Other ID Marks Strongly fluorescent light blue in shortwave ultraviolet light. Some crystals fluoresce a dull red in longwave.
In Group Silicates; Cyclosilicates
Striking Features Color, crystal habits, locality, and mineral associations
Environment In a hydrothermal replacement deposit composed of Natrolite veins in Glaucophane schist in Serpentine.
Rock Type Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 3
Demand (1-3) 1


Benitoite AUCTIONS



USES
Benitoite is cherished by collectors as a rare and valuable mineral. It is also cut as as an exquisite rare gemstone.

NOTEWORTHY LOCALITIES
The only significant locality for Benitoite is the Diablo Range, near the headwaters of the San Benito River, in the Southern tip of San Benito Co., California. Virtually all collectors specimens for this mineral are from this area. The now-closed Dallas Gem Mine in the Diablo Range has been the source of most of the available material and the largest crystals. Other localities in the area include the Santa Rita Peak, the Victor Claim, the Number One Mine, and the Junnila Mine. In Japan, a very limited occurrence of small gemmy Benitoite is Hashidate, Itoigawa, Niigata Prefecture, Japan.

COMMON MINERAL ASSOCIATIONS
Natrolite, Neptunite, Serpentine, Albite, Glaucophane, Joaquinite, Crossite

DISTINGUISHING SIMILAR MINERALS
The crystal habits, color, and locality are able to distinguish Benitoite from all other minerals.


benitoite PHOTOS
 
ADDITIONAL RESOURCES
 
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