orthorhombic
Topaz
Al2SiO4(F,OH)2
Quick Facts
Hardness
8
Specific Gravity
3.50-3.57
Refractive Index
1.619-1.627
Crystal Structure
orthorhombic[mmm]:{110}@1.0 + {120}@0.8 + {001}@0.6 orthorhombic
mmm
{110} {120} {001}
Physical Properties
Crystal Systemorthorhombic
Hardness (Mohs)8
Specific Gravity3.50-3.57
CleavagePerfect basal {001}
FractureConchoidal
LustreVitreous
Optical Properties
Refractive Index1.619-1.627
Birefringence0.008
PleochroismWeak to distinct (varies by colour)
Dispersion0.014
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