triclinic Tectosilicates
Labradorite
Formula (Ca,Na)(Al,Si)4O8
Crystal Structure
triclinic[-1]:{010}@1.0 + {001}@0.8 + {110}@0.6 | phenomenon[labradorescence] triclinic
-1
{010} {001} {110}
Quick Facts
Hardness
6.0
Specific Gravity
2.69
Refractive Index
1.559
Optical Character
Biaxial +
Physical Properties
- Crystal System
- triclinic
- Hardness (Mohs)
- 6.0
- Specific Gravity
- 2.69
- Cleavage
- Perfect in two directions at ~90 degrees
- Fracture
- Uneven to conchoidal
- Lustre
- Vitreous to pearly
Optical Properties
- Refractive Index
- 1.559
- Birefringence
- 0.008-0.010
- Optical Character
- Biaxial +
- Dispersion
- 0.012
- Pleochroism
- None to weak
- Phenomenon
- Labradorescence
Characteristics
Colours
Grey body with blue flashGrey body with green flashGrey body with gold flashGrey body with purple flashSpectral colours (Spectrolite)Rainbow flashes
Localities
MadagascarCanada (Labrador - type locality)Finland (Spectrolite)MexicoRussiaAustralia
Common Inclusions
Twin lamellae (cause of phenomenon)Exsolution lamellaeMagnetite inclusionsGrowth features
Known Treatments
Generally not treated
Crystal Forms
pinacoidprism
Related Minerals
Other minerals in the triclinic system
