hexagonal Cyclosilicates
Heliodor
Formula Be3Al2(SiO3)6:Fe3+
Crystal Structure
#! Species: Heliodor (Beryl)
#! System: Hexagonal (6/mmm)
#! Habit: Elongated hexagonal prism with second-order prism
hexagonal[6/mmm]:{10-10}@1.0 + {0001}@0.3 + {11-20}@0.2 | elongate(c:2.0)
hexagonal
6/mmm
{10-10} {0001} {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
- 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: Yellow / Pale yellow (Subtle; similar to other yellow beryls)
Characteristics
Colours
YellowGolden yellowGreenish-yellowPale yellowLemon yellow
Localities
BrazilMadagascarNamibiaUkraineNigeriaRussia (Urals)
Common Inclusions
Liquid feathersGrowth tubesTwo-phase inclusionsParallel tubes (rain)
Known Treatments
Heat treatment (can lighten or modify colour)Irradiation (rare)
Crystal Forms
hexagonal_prismpinacoiddihexagonal_prism
Related Minerals
Other minerals in the hexagonal system
