Table / list of Hardness, Specific Gravity, Refractive Index, Chemical formula, Crystal Structure, Mineral, Birthstone of Gemstones


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Gemstone Specific Gravity Mohs Hardness Refractive Index Chemical Formula Gemstone Mineral Crystal Structure Birthstone Month
Achorite 3.03 - 3.25 7.0 - 7.5 1.610-1.661 (NaCa)(LI,MgFe,Al)
9B3Si6(O,OH)31 		Tourmaline Hexagonal October
Agate 2.65 7.0 1.530 - 1.550 SiO2 Quartz Hexagonal -
Alexandrite 3.68 - 3.78 8.5 1.746 - 1.755 BeAl2O4 Chrysoberyl Orthorhombic June
Almandine 3.50 - 4.30 6.5 - 7.5 1.750 - 1.830 Fe2+3Al2Si3O12 Garnet Isometric January
Almandine Spinel 3.58 - 4.06 8.0 1.708 - 1.735 MgAl2O4 Spinel Isometric -
Almandine-Spessartine 3.50 - 4.30 6.5 - 7.5 1.750 - 1.830 Mn(II)3Al2(SiO4)3 Garnet Isometric January
Amazonite 2.55 - 2.76 6.0 - 6.5 1.518 - 1.526 KAlSi3O8 Feldspar Triclinic -
Amethyst 2.65 7.0 1.532 - 1.554 SiO2 Quartz Hexagonal February
Andradite 3.50 - 4.30 6.5 - 7.5 1.880 - 1.940 Ca3Fe2(SiO4)3 Garnet Isometric January
Aquamarine 2.63 - 2.91 7.5 - 8.0 1.567-1.590 Be3Al2(SiO3)6 Beryl Hexagonal March
Balas Ruby 3.58 - 4.06 8.0 1.708 - 1.735 MgAl2O4 Spinel Isometric July
Black Opal 1.98 - 2.25 5.5 - 6.5 1.440 - 1.460 SiO2nH2O Opal Amorphous October
Bloodstone 2.65 7.0 1.535 - 1.539 SiO2 Quartz Trigonal March
Brazilian Emerald 3.03 - 3.25 7.0 - 7.5 1.610 - 1.640 Be3Al2(SiO3)6 Tourmaline Hexagonal October
Cairngorm 2.65 7.0 1.540 - 1.550 SiO2 Quartz Trigonal -
Carnelian 2.65 7.0 1.530 - 1.550 SiO2 Quartz Trigonal July
Cat's Eye 3.68 - 3.78 8.5 1.746 - 1.755 BeAl2O4 Chrysoberyl Orthorhombic -
Chalcedony 2.65 7.0 1.544 - 1.553 SiO2 Quartz Trigonal -
Chlor spinel 3.58 - 4.06 8.0 1.712 - 1.717 MgAl2O4 Spinel Isometric July
Chrome Pyrope 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 Mg3Al2(SiO4)3 Garnet Cubic January
Chrysoberyl 3.68 - 3.78 8.5 1.746 - 1.755 BeAl2O4 Chrysoberyl Orthorhombic -
Chrysoprase 2.65 7.0 1.530 - 1.550 SiO2 Quartz Trigonal -
Citrine 2.65 7.0 1.532 - 1.554 SiO2 Quartz Trigonal November
Color-Change Garnet 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 Nesosilicate Garnet Cubic January
Demantoid 3.50 - 4.30 6.5 - 7.5 1.880 - 1.900 Ca3Fe2Si3O12 Garnet Cubic January
Diamond 3.51 10 2.417 C Diamond Cubic April
Dravite 3.03 - 3.25 7.0 - 7.5 1.610-1.661 NaMg3(Al,Fe)
6Si6O18(BO3)3
(OH)4 		Tourmaline Trigonal October
Emerald 2.63 - 2.91 7.5 - 8.0 1.560 - 1.605 Be3Al2(SiO3)6 Beryl Hexagonal May
Feldspar 2.55 - 2.76 6.0 - 6.5 1.518 - 1.572 KAlSi3O8 –NaAlSi3O8 –CaAl2Si2O8 Feldspar triclinic or
monoclinic		 -
Fire Opal 1.98 - 2.25 5.5 - 6.5 1.430 - 1.460 SiO2nH2O Opal Amorphous October
Garnet 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 X3Y2(SiO4)3 Garnet Cubic January
Gahnospinel 3.58 - 4.06 8.0 1.712 - 1.747 (Mg,Zn)Al2O4 Spinel -
Goshenite 2.63 - 2.91 7.5 - 8.0 1.570 - 1.600 Be3Al2Si6O18 Beryl Hexagonal -
Green Quartz 2.65 7.0 1.540-1.550 SiO2 Quartz Hexagonal -
Grossular 3.50 - 4.30 6.5 - 7.5 1.880 - 1.940 Ca3Al2(SiO4)3 Garnet Cubic -
Heliodor 2.63 - 2.91 7.5 - 8.0 1.570 - 1.600 Al2Be3(Si6O16) Beryl Hexagonal -
Heliotrope 2.65 7.0 1.535 - 1.539 SiO2 Quartz Trigonal -
Hessonite 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 Ca3Al2Si3O12 Garnet Cubic January
Hyacinth 4.60 - 4.70 7.5 1.777 - 1.987 ZrSiO4 Zircon Tetragonal -
Indicolite 3.03 - 3.25 7.0 - 7.5 1.610 - 1.640 Na(Li,Al)3Al6Si6O18(BO3)3(OH)4 Tourmaline Trigonal October
Jade 2.90 - 3.10 6.0 1.640 - 1.667 NaAl(SiO3)2 Jade Monoclinic March
Jadeite 2.90 - 3.10 6.0 1.640 - 1.667 NaAl(SiO3)2 Jade Monoclinic March
Jargoon 4.60 - 4.70 7.5 1.777 - 1.987 ZrSiO4 Zircon Tetragonal December
Jasper 2.65 7.0 1.540 - 1.550 SiO2 Quartz Trigonal October
Labradorite 2.55 - 2.76 6.0 - 6.5 1.560 - 1.572 NaAlSi3O8 Feldspar Triclinic June
Lapis Lazuli 2.70 - 2.90 5.0 - 5.5 1.500 - 1.550 Mixture Lapis Lazuli None September
Malaia 3.50 - 4.30 6.5 - 7.5 1.880 - 1.940 (Mg,Mn)3Al2(SiO4)3 Garnet Cubic January
Matura Diamond 4.60 - 4.70 7.5 1.777 - 1.987 ZrSiO4 Zircon Tetragonal December
Moonstone 2.55 - 2.76 6.0 - 6.5 1.518 - 1.526 (Na,K)AlSi3O8 Feldspar None June
Morganite 2.63 - 2.91 7.5 - 8.0 1.585 - 1.594 Be3Al2(Si6O18) Beryl Hexagonal -
Morion 2.65 7.0 1.540 - 1.550 SiO2 Quartz Trigonal -
Nephrite 2.90 - 3.10 6.0 1.600 - 1.641 Ca2(Mg,Fe)5Si8O22(OH)2 Jade Monoclinic -
Onyx 2.65 7.0 1.531 - 1.539 SiO2 Quartz Trigonal August
Opal 1.98 - 2.25 5.5 - 6.5 1.440 - 1.460 SiO2nH2O Opal Amorphous October
Orthoclase 2.55 - 2.76 6.0 - 6.5 1.518 - 1.526 Feldspar -
Peridot 3.22 - 3.45 7.0 1.635 - 1.690 Peridot August
Peristerite 2.55 - 2.76 6.0 - 6.5 1.560 - 1.572 Feldspar -
Praziolite 2.65 7.0 1.540 - 1.550 SiO2 Quartz Trigonal -
Pyrope 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 Mg3Al2(SiO4)3 Garnet Cubic January
Pyrope-Almandine 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 Mg3Al2(SiO4)3 Garnet Cubic January
Pyrope-Spessartine 3.50 - 4.30 6.5 - 7.5 1.730 - 1.760 Mg3Al2(SiO4)3 Garnet Cubic January
Quartz 2.65 7.0 1.544 - 1.553 Quartz Trigonal -
Red Beryl 2.63 - 2.91 7.5 - 8.0 1.570 - 1.598 Beryl Hexagonal -
Rhodolite 3.50 - 4.30 6.5 - 7.5 1.740 - 1.770 Garnet Cubic January
Rock Crystal 2.65 7.0 2.000 SiO2 Quartz Trigonal -
Rose Quartz 2.65 7.0 1.540 - 1.550 SiO2 Quartz Trigonal -
Rubellite 3.03 - 3.25 7.0 - 7.5 1.610 - 1.640 Tourmaline Trigonal October
Rubicelle 3.58 - 4.06 8.0 1.712 - 1.717 MgAl2O4 Spinel -
Ruby 3.96 - 4.05 9.0 1.757 - 1.779 Al2O3:Cr Corundum July
Sapphire 3.96 - 4.05 9.0 1.757 - 1.779 Al2O3 Corundum September
Sapphire Spinel 3.58 - 4.06 8.0 1.712 - 1.747 MgAl2O4 Spinel -
Siberite 3.03 - 3.25 7.0 - 7.5 1.625-1.675 Tourmaline Hexagonal October
Smoky Quartz 2.65 7.0 1.540 - 1.550 SiO2 Quartz Trigonal -
Spessartine 3.50 - 4.30 6.5 - 7.5 1.790 - 1.810 Garnet Cubic January
Spinel 3.58 - 4.06 8.0 1.712 - 1.717 MgAl2O4 Spinel -
Sunstone 2.55 - 2.76 6.0 - 6.5 1.560 - 1.572 Feldspar June
Topaz 3.50 - 3.60 8.0 1.607 - 1.627 Al2SiO4(F,OH)2 Topaz November
Topazolite 3.50 - 4.30 6.5 - 7.5 1.880 - 1.940 Ca3Fe2(SiO4)3 Garnet Cubic January
Tourmaline 3.03 - 3.25 7.0 - 7.5 1.603 - 1.655 (Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4 Tourmaline Trigonal October
Tsavorite 3.50 - 4.30 6.5 - 7.5 1.739 - 1.744 Ca3Al2Si3O12 Garnet Cubic January
Turquoise 2.60 - 2.80 5.0 - 6.0 1.610 - 1.650 CuAl6(PO4)4(OH)84H2O Turquoise December
Uvarovite 3.50 - 4.30 6.5 - 7.5 1.740 - 1.870 Ca3Cr2Si3O12 Garnet Cubic January
Verdilite 3.03 - 3.25 7.0 - 7.5 1.612-1.638 (Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4 Tourmaline Trigonal October
Water Opal 1.98 - 2.25 5.5 - 6.5 1.440 - 1.460 SiO2nH2O Opal Amorphous October
White Opal 1.98 - 2.25 5.5 - 6.5 1.440 - 1.460 SiO2nH2O Opal Amorphous October
Zircon 4.60 - 4.70 7.5 1.777 - 1.987 ZrSiO4 Zircon Tetragonal December


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