Compact granular natrolite veins cutting a grayish green fibrous shist interlayered with serpentine.
IMA Status:
Valid Species (Pre-IMA) 1907
Locality:
Benitoite Gem mine, head waters of the San Benito river, 1 mile south of Santa Rita Peak, San Benito County, California, USA Link to MinDat.org Location Data.
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Physical Properties of Benitoite
Cleavage:
{1011} Poor
Color:
Blue, Purple, Pink, White, Colorless.
Density:
3.6
Diaphaneity:
Transparent to translucent
Fracture:
Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit:
Tabular - Form dimensions are thin in one direction.
Hardness:
6-6.5 - Orthoclase-Pyrite
Luminescence:
Fluorescent, Short UV=blue.
Luster:
Vitreous (Glassy)
Magnetism:
Nonmagnetic
Streak:
white
Optical Properties of Benitoite
Gladstone-Dale:
CI meas= -0.013 (Superior) - where the CI = (1-KPDmeas/KC) CI calc= 0.028 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2081,KPDmeas= 0.2168,KC= 0.2141 Ncalc = 1.77 - 1.8
Optical Data:
Uniaxial (+), w=1.757, e=1.804, bire=0.0470.
Calculated Properties of Benitoite
Electron Density:
Bulk Density (Electron Density)=3.34 gm/cc note: Specific Gravity of Benitoite =3.60 gm/cc.
Fermion Index:
Fermion Index = 0.08 Boson Index = 0.92
Photoelectric:
PEBenitoite = 146.17 barns/electron U=PEBenitoite x rElectron Density= 488.71 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Benitoite is Not Radioactive
Chemical Formula: 
