monoclinic Tectosilicates
Sanidine (Tabular)
Formula (K,Na)AlSi3O8
Crystal Structure
#! Species: Sanidine
#! System: Monoclinic (2/m)
#! Habit: Tabular on {010} with Carlsbad twinning
monoclinic[2/m]:{010}@1.0 + {001}@0.8 + {110}@0.6
monoclinic
2/m
{010} {010} {001} {110}
Quick Facts
Hardness
6.0
Specific Gravity
2.52
Refractive Index
1.518
Optical Character
Biaxial -
Physical Properties
- Crystal System
- monoclinic
- Hardness (Mohs)
- 6.0
- Specific Gravity
- 2.52
- Cleavage
- Perfect {001} and good {010}
- Fracture
- Uneven to conchoidal
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.518
- Birefringence
- 0.007
- Optical Character
- Biaxial -
Characteristics
Colours
ColorlessPale yellowGrey
Localities
Germany (Eifel)Italy (Vesuvius)MadagascarMexico
Common Inclusions
Twin lamellae (Carlsbad twin common)
Known Treatments
None
Crystal Forms
pinacoidprism
Notes
High-temperature polymorph; orthoclase is the medium-temperature equivalent
Related Minerals
Other minerals in the monoclinic system
