Source: San Benito County, California, USA (only known source)

Chemical: BaTiSi3O9 (barium titanium silicate)

Formation: Forms in a veins of natrolite in a serpentine formation.

Crystal System: Hexagonal

Unusual Properties: Seldom seen as a gemstone due to extreme rarity and overall small sizes of cutable material. Estimates from one source tells me that only about 5,000 carats of cutable benitoite has been taken from the ground. The photo above is a 1.11 carat specimen in Your Gemologist’s collection. The unusual property of this stone is that it will fluoresce bright blue to short wave ultraviolet light as seen below.

Colors: Colorless, blue and rarely pink

Wearability: With a hardness of 6-6.5 it would be comparable to a tanzanite for wear and tear in jewelry.

Gemological Information:

RI: 1.757 – 1.804

Birefringence: .047

Optical Character: U+

SG: 3.64

Hardness: 6 – 6.5



Shown above is a rock from a mine run of benitoite ore. Photo#1 is the rock showing the light blue benitoite crystals in matrix with the neptunite crystals (black) the natrolite skin mineral (white) and the native host rock. Photo #2 is a close up of the benitoite (blue) crystals. Photo #3 is this same area under short wave ultraviolet light. All photos by Robert James FGA, GG.

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