trigonal Tectosilicates
Quartz (Japan Law Twin)
Formula SiO2
Crystal Structure
#! Species: Quartz
#! System: Trigonal (32)
#! Habit: Japan Law contact twin at 84°33'
trigonal[32]:{10-10}@0.5 + {10-11}@1.2 + {01-11}@1.0 + {0001}@2.0 | elongate(c:2.0) | twin(japan)
trigonal
32
{10-10} {10-11} {01-11} {0001}
Quick Facts
Hardness
7.0
Specific Gravity
2.65
Refractive Index
1.544
Optical Character
Uniaxial +
Physical Properties
- Crystal System
- trigonal
- Hardness (Mohs)
- 7.0
- Specific Gravity
- 2.65
- Cleavage
- None
- Fracture
- Conchoidal
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.544
- Birefringence
- 0.009
- Optical Character
- Uniaxial +
- Dispersion
- 0.013
- Pleochroism
- None (in colourless)
Characteristics
Colours
Colourless (rock crystal)White (milky)Various (see variety gemstones)
Localities
BrazilMadagascarUSAAlpsWorldwide
Common Inclusions
Two-phase fluid inclusionsNegative crystalsRutile needlesTourmaline crystalsVarious mineral inclusions
Known Treatments
Heat treatmentIrradiationCoating
Crystal Forms
prismrhombohedrontwin
Diagnostic Features
Conchoidal fracture; lacks cleavage; hexagonal cross-section with horizontal striations on prism
Synthetics & Simulants
Known synthetic and simulant versions of Quartz
Related Minerals
Other minerals in the trigonal system
