monoclinic Inosilicates
Hiddenite
Formula 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 +
Physical Properties
- Crystal System
- monoclinic
- Hardness (Mohs)
- 6.5
- Specific Gravity
- 3.15
- Cleavage
- Perfect in two directions (spodumene cleavage)
- Fracture
- Uneven to splintery
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.66
- Birefringence
- 0.014-0.016
- Optical Character
- Biaxial +
- Dispersion
- 0.017
- Pleochroism
- strong: Blue-green / Emerald green / Yellow-green (Trichroic; cutters orient to show best green face-up)
Characteristics
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
Related Minerals
Other minerals in the monoclinic system
