triclinic Tectosilicates
Sunstone
(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 Systemtriclinic
Hardness (Mohs)6.0
Specific Gravity2.62
CleavagePerfect in two directions at ~90 degrees
FractureUneven to conchoidal
LustreVitreous
Optical Properties
Refractive Index1.537
Birefringence0.007-0.010
Optical CharacterBiaxial +
Dispersion0.012
Pleochroismmoderate: Red / Green (Oregon copper sunstone only; dramatic red-green dichroism in saturated stones)
PhenomenonAventurescence
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
