Return to CD Index
Properties of Commonly Faceted Minerals and Materials

Material Refractive
Index
Critical
Angle
Birefringenge Dispersion Hardness Specific
Gravity
Crystal
System
Class Formula Cleavage
Apatite series 1.64 37.57 .004 .013 5.0 3.05-3.20 hexagonal 6/m Ca5(PO4,CO3)3(F,Cl,OH) 2; {0001}indistinct; {10-10} trace
Beryl 1.57-1.60 38.68-39.56 .006-.009 .014 7.5-8.0 2.60-2.90 hexagonal 6/m 2/m 2/m Be3Al2Si6O18 1; {0001} indistinct
Color varieties of beryl include aquamarine (blue), emerald (green), goshenite (colorless), heliodor (yellow) and morganite (pink).
Chrysoberyl 1.75 34.85 .010 .015 8.5 3.75 orthorhombic 2/m 2/m 2/m BeAl2O4 3; {110} distinct, {010} imperfect, {001} indistinct
Corundum 1.77 34.40 .008 .018 9.0 4.00-4.10 hexagonal B3 2/m Al2O3 2; {0001} and {10-11} parting
Ruby is red corundum. All other colors of corundum are classified as sapphires.
Cubic Zirconia 2.15-2.18 27.30-27.72 .000 .058-.060 8.3-8.5 5.6-6.0 (man made)   ZrO2  
Danburite 1.63 37.84 .006 .016 7.0 2.97-3.02 orthorhombic 2/m 2/m 2/m CaB2(SiO4)2 1; {001} indistinct
Diamond 2.41 24.52 .000 .044 10.0 3.51 isometric 4/m B3 2/m C 1; {111} perfect
Epidote 1.75 34.85 .047 .030 6.0-7.0 3.35-3.50 monoclinic 2m Ca2(Fe,Al)3(Si2O7)(SiO4)(O,OH_2 6; {001} and {010} perfect, {100}, {110}, {-110} and {-201} partings
Feldspar
Group
1.52-1.58 39.23-41.12 .007-.013 .012            
- orthoclase ~ ~ ~ ~ 6.0-6.5 2.55-2.63 monoclinic 2m KAlSi3O8 2; {11-20} and {10-11} indistinct
- labradorite ~ ~ ~ ~ 6.0-6.5 2.69-2.72 triclinic B1 Na.5-.3Ca.5-.7Al1.5-1.7Si2.5-2.3)8 3; {001} perfect, {010} and {110} nearly perfect
- Sunstone (oligoclase) ~ ~ ~ ~ 6.0-6.5 2.63-2.67 triclinic B1 70-90%(Na,Ca)Al(Al,Si)Si2O810-30%CaAl2Si2O8 3; {001} perfect, {010} nearly perfect, {110} imperfect
Fluorite 1.43 44.37 .000 .007 4.0 3.218 isometirc 4/m B3 2/m CaF2 1; {111} perfect
Garnet Group
- almandine 1.78-1.81 33.54-34.18 .000 .024 7.0-7.5 4.10-4.30 isometric 4/m B3 2/m Fe3Al2(SiO4)3 1; {110} parting sometimes distinct
- andradite 1.85-1.89 31.94-32.74 .000 .057 6.5-7.0 3.70-4.10 isometric 4/m B3 2/m Ca3Fe2(SiO4)3  
- grossular 1.73-1.74 35.08-35.31 .000 .027 6.5-6.7 3.40-3.60 isometric 4/m B3 2/m Ca3Al2(SiO4)3 1; {110} parting
- pyrope 1.73-1.76 34.62-35.31 .000 .022 7.0-7.5 3.50-3.80 isometric 4/m B3 2/m Mg3Al2(SiO4)3 1; {110} parting sometimes distinct
- spessartine 1.79-1.81 33.54-33.96 .000 .027 7.0-7.5 3.80-4.25 isometric 4/m B3 2/m Mn3Al2(SiO4)3 1; {110} parting sometimes distinct
- uvarovite 1.87 32.33 .000   6.5-7.0 3.40-3.80 isometric 4/m B3 2/m Ca3Cr2(SiO4)3  
Glass 1.44-1.68 36.53-43.98     4.0-7.0 2.2-5.0 (man made)   higly variable  
Iolite (cordierite) 1.55 40.18 .017 .017 7.0-7.5 2.53-2.78 orthorhombic 2/m 2/m 2/m Mg2Al4Si5O18 3; {010} distinct, {001} and {100} indistinct
Opal 1.45 43.60 .000   5.5-6.5 1.99-2.25 (amorphous)   SiO2(nH20)  
Peridot (forsterite) 1.67 36.78 .038 .020 7.0 3.28 orthorhombic 2/m 2/m 2/m Mg2SiO4 2; {010} and {100} imperfect
Quartz 1.54 40.49 .009 .013 7.0 2.66 hexagonal 32 SiO2 7; {10-11}{01-11}{10-10}{0001}{11-20}{11-21}{51-61} indistinct
Scapolite series 1.58 39.27 .022 5.5-6.0 2.50-2.78 tetragonal 4/m (Na,Ca)4Al3Si9O24Cl 2; {100} and {110} distinct
Sphene (titanite) 1.99-2.03 29.51-30.17 .051 .051 5.0-5.5 3.45-3.55 monoclinc 2/m CaTiSiO5 2; {110} distinct, {221} parting
Spinel 1.72 35.55 .000 .020 7.5-8.0 3.58 orthorhombic 4/m B3 2/m MgAl2O4 1; {111} parting indistinct
Tanzanite (zoisite) 1.70 36.03 .006 .030 6.5-7.0 3.55 orthorhombic 2/m 2/m 2/m Ca2Al3(SiO4)3(OH) 2; {100} perfect, {010} imperfect
Topaz 1.61 38.40 .008 .014 8.0 3.49-3.57 orthorhombic 2/m 2/m 2/m Al2SiO4(F,OH)2 1; {001} perfect
Tourmaline
Group
1.62-1.65 37.31-38.40 .014-.044 .017            
- dravite ~ ~ ~ ~ 7.0 3.03 hexagonal 3m NaMg3Al6(BO3)3Si6O18(OH)4 2; {11-20} and {10-11} indistinct
- elbaite ~ ~ ~ ~ 7.0 3.03-3.10 hexagonal 3m Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 2; {11-20} and {10-11} indistinct
- liddicoatite ~ ~ ~ ~ 7.5 3.02 hexagonal 3m Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4  
- uvite ~ ~ ~ ~ 7.5 3.04 hexagonal 3m (Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4  
Zircon 1.94 31.03 .060 .038 7.5 4.60-4.70 tetragonal 4/m 2/m 2/m ZrSiO4 2; {110} imperfect; {111} poor
Return to CD Index