Mineral Information and Data:

Benitoite
BaTiSi3O9 [CNMNC approved formula]

Named for the occurrence in San Benito Co., California, USA.

IMA status : Valid species (Pre-IMA 1907) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
59.01.01.02  
  (59) Cyclosilicate Three-Membered Rings
  (59.01) anhydrous, no other anions
  (59.01.01) Benitoite group
  
Nickel-Strunz
(10th edition) :
09.CA.05
  (09) Silicates
  (09.C) Cyclosilicates
  (09.CA) [Si3O9]6- 3-membered single rings (dreier-Einfachringe), without insular complex anions
  
Crystal system: Hexagonal System
Point group (H-M): 6m2 (or 6m2) — ditrigonal-dipyramidal
Space group: P62c
Unit cell: a = 6.6410(7)Å, c = 9.7597(10) Å, Z=2
Crystal Habit: Flat pyramidal crystals, tabular on {0001}, triangular or hexagonal in outline, to 6 cm.
Twinning: By rotation about [0001]
  
Color: Sapphire-blue, white to colorless, pink; commonly bicolored
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 6 - 6.5
Measured Density: 3.65 g/cm3
Cleavage: Poor on {1011}
Fracture: Conchoidal
  
Geologic Setting: In natrolite veins cutting glaucophane schist in a serpentine body (San Benito Co., California, USA); in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting serpentinite (Ohmi, Japan).
Mineral Association: Neptunite, joaquinite, natrolite (San Benito Co., California, USA); ohmilite, bario-orthojoaquinite, leucosphenite (Ohmi, Japan)
  
Other Properties: Gemstone Rare.

 

Benitoite
Benitoite on natrolite coated matrix.
Origin: Gem mine, San Benito Co., California, U.S.A.
Sample size: 5.6 x 3.5 x 2.3 cm, crystals to 15 mm
Photo: Dan Weinrich

 

Benitoite
(zoom-in of above)

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