triclinic Tectosilicates
Sunstone
Formula (Na,Ca)(Al,Si)4O8
Crystal Structure
#! Species: Sunstone (Plagioclase Feldspar)
#! System: Triclinic (-1)
#! Habit: Tabular with aventurescent copper/hematite platelets
triclinic[-1]:{010}@1.0 + {100}@0.9 + {001}@0.7 + {110}@0.5 | phenomenon[aventurescence]
triclinic
-1
{010} {100} {001} {110}
Quick Facts
Hardness
6.0
Specific Gravity
2.62
Refractive Index
1.537
Optical Character
Biaxial +
Physical Properties
- Crystal System
- triclinic
- Hardness (Mohs)
- 6.0
- Specific Gravity
- 2.62
- Cleavage
- Perfect in two directions at ~90 degrees
- Fracture
- Uneven to conchoidal
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.537
- Birefringence
- 0.007-0.010
- Optical Character
- Biaxial +
- Dispersion
- 0.012
- Pleochroism
- moderate: Red / Green (Oregon copper sunstone only; dramatic red-green dichroism in saturated stones)
- Phenomenon
- Aventurescence
Characteristics
Colours
OrangeRedGoldGreen (Oregon)PinkColorlessBicolourTricolour
Localities
Oregon (USA)NorwayIndiaTanzaniaRussiaCanada
Common Inclusions
Copper platelets (Oregon)Hematite platelets (India, Norway)Goethite plateletsSchiller inclusions
Known Treatments
Generally not treated
Crystal Forms
pinacoidprism
Related Minerals
Other minerals in the triclinic system
