triclinic Nesosilicates
Kyanite
Formula Al2SiO5
Crystal Structure
#! Species: Kyanite
#! System: Triclinic (-1)
#! Habit: Bladed with directional colour zoning
triclinic[-1]:{100}@1.0[colour_zone:directional] + {010}@0.4 + {001}@1.5 + {110}@0.6
triclinic
-1
{100} {010} {001} {110}
Quick Facts
Hardness
4.0
Specific Gravity
3.53
Refractive Index
1.716
Optical Character
Biaxial -
Physical Properties
- Crystal System
- triclinic
- Hardness (Mohs)
- 4.0
- Specific Gravity
- 3.53
- Cleavage
- Perfect {100}, good {010}
- Fracture
- Splintery
- Lustre
- Vitreous to pearly
Optical Properties
- Refractive Index
- 1.716
- Birefringence
- 0.012-0.017
- Optical Character
- Biaxial -
- Dispersion
- 0.02
- Pleochroism
- strong: Colourless to pale blue / Deep blue (Strong pleochroism visible in different crystallographic directions)
Characteristics
Colours
Blue (classic)Blue with colorless zonesGreenOrange (rare)ColorlessGray
Localities
Nepal (gem quality)BrazilKenya (green)SwitzerlandIndiaUSA (North Carolina)
Crystal Forms
pinacoidbladed crystals
Diagnostic Features
Directional hardness (4-7); blue bladed crystals; triclinic; perfect cleavage {100}
Notes
Diagnostic variable hardness; often contains color zoning; parting on {001}; good toughness despite cleavage
Related Minerals
Other minerals in the triclinic system
