trigonal Oxides
Ruby
Al2O3:Cr
Quick Facts
Hardness
9.0
Specific Gravity
4.0
Refractive Index
1.762
Optical Character
Uniaxial -
Crystal Structure
#! Species: Ruby (Corundum)
#! System: Trigonal (-3m)
#! Habit: Tabular with dipyramid and oriented silk
trigonal[-3m]:{10-11}@1.0[silk:oriented] + {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
Optical CharacterUniaxial -
Dispersion0.018
Pleochroismstrong: Purplish-red / Orange-red (Best seen in thick stones; dichroism key to separating from red spinel)
FluorescenceModerate to strong red (LWUV); weaker under SWUV
Colours
RedPinkish-redPurplish-red
Localities
MyanmarMozambiqueThailandMadagascar
Common Inclusions
SilkCrystalsFingerprintsColor zoning
Known Treatments
Heat treatmentGlass fillingFlux healing
Crystal Forms
dipyramidpinacoid
Diagnostic Features
Strong red fluorescence (LWUV); silk (rutile needles at 60°); absorption at 694nm doublet
Interactive Preview
Open this crystal in the CDL Playground to rotate, export, and explore in 3D.
Open in Playground #! Species: Ruby (Corundum)
#! System: Trigonal (-3m)
#! Habit: Tabular with dipyramid and oriented silk
trigonal[-3m]:{10-11}@1.0[silk:oriented] + {0001}@0.4
Synthetics & Simulants
Known synthetic and simulant versions of Ruby
Related Minerals
Other minerals in the trigonal system
