monoclinic Inosilicates
Hiddenite
LiAlSi2O6:Cr
Crystal Structure
#! Species: Hiddenite (Spodumene)
#! System: Monoclinic (2/m)
#! Habit: Prismatic with strong green pleochroism
monoclinic[2/m]:{110}@1.0 + {100}@0.7 + {001}@1.0[pleochroism:strong]
monoclinic
2/m
{110} {100} {001}
Quick Facts
Hardness
6.5
Specific Gravity
3.15
Refractive Index
1.66
Optical Character
Biaxial +
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Open in PlaygroundPhysical Properties
Crystal Systemmonoclinic
Hardness (Mohs)6.5
Specific Gravity3.15
CleavagePerfect in two directions (spodumene cleavage)
FractureUneven to splintery
LustreVitreous
Optical Properties
Refractive Index1.66
Birefringence0.014-0.016
Optical CharacterBiaxial +
Dispersion0.017
Pleochroismstrong: Blue-green / Emerald green / Yellow-green (Trichroic; cutters orient to show best green face-up)
Colours
Emerald green (Cr-colored, rare)Yellow-greenLight greenBlue-green
Localities
USA (North Carolina - type locality)Brazil (light green, may be V-colored)MadagascarAfghanistan
Common Inclusions
Growth tubesEtch tubesHealing cracksLiquid inclusionsMulti-phase inclusions
Known Treatments
Irradiation (to enhance colour)
Crystal Forms
prismpinacoid
Notes
True Cr-colored hiddenite is extremely rare and valuable; many stones sold as hiddenite are lighter colored or V-bearing
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Open in PlaygroundRelated Minerals
Other minerals in the monoclinic system
