hexagonal Cyclosilicates
Beryl (Tabular)
Formula Be3Al2Si6O18
Crystal Structure
#! Species: Beryl
#! System: Hexagonal (6/mmm)
#! Habit: Tabular with dominant pinacoid
hexagonal[6/mmm]:{0001}@1.0 + {10-10}@0.6 + {11-20}@0.2
hexagonal
6/mmm
{0001} {10-10} {11-20}
Quick Facts
Hardness
7.5
Specific Gravity
2.67
Refractive Index
1.577
Optical Character
Uniaxial -
Physical Properties
- Crystal System
- hexagonal
- Hardness (Mohs)
- 7.5
- Specific Gravity
- 2.67
- Cleavage
- Imperfect basal (rarely seen)
- Fracture
- Conchoidal to uneven
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.577
- Birefringence
- 0.005-0.009
- Optical Character
- Uniaxial -
- Dispersion
- 0.014
- Pleochroism
- Weak to distinct (varies by variety)
Characteristics
Colours
Green (emerald)Blue (aquamarine)Pink (morganite)Yellow (heliodor)Colorless (goshenite)Red (red beryl)
Localities
ColombiaBrazilZambiaPakistanMadagascarAfghanistanRussia (Urals)Nigeria
Common Inclusions
Three-phase (Colombian emerald)Actinolite needles (Zambian emerald)Rain/parallel tubes (aquamarine)Liquid feathersTwo-phase inclusionsMineral crystals
Known Treatments
Oiling (emerald)Heat treatment (aquamarine, morganite)Fracture filling (emerald)
Crystal Forms
pinacoidhexagonal_prismdihexagonal_prism
Related Minerals
Other minerals in the hexagonal system
