trigonal
Ruby
Al2O3:Cr
Quick Facts
Hardness
9.0
Specific Gravity
4.0
Refractive Index
1.762
Crystal Structure
trigonal[-3m]:{10-11}@1.0 + {0001}@0.4 trigonal
-3m
{10-11} {0001}
Physical Properties
Crystal Systemtrigonal
Hardness (Mohs)9.0
Specific Gravity4.0
CleavageNone (parting on {0001})
FractureConchoidal to uneven
LustreVitreous to adamantine
Optical Properties
Refractive Index1.762
Birefringence0.008
PleochroismStrong (purplish-red/orange-red)
Dispersion0.018
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