Benitoite
Species
Legendary · BaTiSi₃O₉
A barium titanium silicate in flat triangular crystals, declared the official state gem of California in 1985, found in gem quality only in the natrolite veins of San Benito County. Under shortwave ultraviolet it glows a strong blue; it is told from sapphire by its stronger birefringence and dispersion and its blue-and-colourless dichroism.
Identity
- Formula
- BaTiSi₃O₉
- Chemical class
- Silicate
Crystallography
- Crystal system
- Hexagonal
- Habits
- Tabular, Triangular
- Fracture
- Conchoidal
Physical properties
- Mohs hardness
- 6.5
- Density
- 3.65 g/cm³
- Luster
- Vitreous
- Colors
- blue, violet-blue, colorless, pink
- Streak
- white
- Transparency
- Transparent
Geology
- Origins
- Hydrothermal
- Host rocks
- Ultramafic rock (peridotite, serpentinite)
- Associated minerals
- Neptunite, Natrolite, Joaquinite
- Geography
- USA (San Benito County, California), Japan, Australia
Classification
- Rarity
- Legendary
- Gem quality
- Yes
Arcane properties
- Affinity
- Light, Storm
- Effects
- Elemental lightning, Warding
- Planar origin
- Material Plane
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Benitoite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- Brendan M. Laurs, William R. Rohtert, Michael Gray, Benitoite from the New Idria District, San Benito County, California. Gemological Institute of America, Gems & Gemology (Fall 1997), 1997.
- Historical Reading List: Benitoite. Gemological Institute of America.
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