hexagonal Cyclosilicates
Heliodor
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 -
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Open in PlaygroundPhysical Properties
Crystal Systemhexagonal
Hardness (Mohs)7.5
Specific Gravity2.67
CleavageImperfect basal
FractureConchoidal to uneven
LustreVitreous
Optical Properties
Refractive Index1.577
Birefringence0.005-0.009
Optical CharacterUniaxial -
Dispersion0.014
Pleochroismweak: Yellow / Pale yellow (Subtle; similar to other yellow beryls)
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
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Open in PlaygroundRelated Minerals
Other minerals in the hexagonal system
