Gemstone Properties
| Name | Structure | Hardness | Specific Gravity | Refractive index | Doubly Refracting (bi-refraction) |
| Achroite Tourmaline | Trigonal | 7.5 | 3.06 | 1.62 - 1.6 | 0.018 |
| Agate | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Albite | Triclinic | 6 | 2.64 | 1.54 - 1.5 | 0.009 |
| Almandine Garnet, Almandite Garnet | Cubic | 7.5 | 4 | 1.76 - 1.8 | None |
| Amber | Amorphous | 2.5 | 1.08 | 1.54 - 1.5 | |
| Amethyst | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Andalusite | Orthorhombic | 7.5 | 3.16 | 1.63 - 1.6 | 0.01 |
| Andradite Garnet | Cubic | 6.5 | 3.85 | 1.85 - 1.8 | None |
| Apatite | Hexagonal | 5 | 3.2 | 1.63- 1.64 | 0.003 |
| Aquamarine | Hexagonal | 7.5 | 2.69 | 1.57 - 1.5 | 0.006 |
| Aragonite | Orthorhombic | 3.5 | 2.94 | 1.53 - 1.6 | 0.155 |
| Aventurine | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Azurite | Monoclinic | 3.5 | 3.77 | 1.73 - 1.8 | 0.11 |
| Benitoite | Hexagonal | 6.5 | 3.67 | 1.76 - 1.8 | 0.047 |
| Bloodstone | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Blue Topaz | |||||
| Brazilianite | Monoclinic | 5.5 | 2.99 | 1.60 - 1.6 | 0.021 |
| Brown Quartz, Smokey Quartz | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Carnelian | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Chalcedony | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Chatoyant Quartz | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Chrome Diopside | Monoclinic | 5.5 | 3.29 | 1.66 - 1.7 | 0.029 |
| Chrome Tourmaline | |||||
| Chrysoberyl | Orthorhombic | 8.5 | 3.71 | 1.74 - 1.7 | 0.009 |
| Chrysoprase | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Citrine | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Color Change Garnet | X3Y2(SiO4)3, | ||||
| Coral | Trigonal | 3 | 2.68 | 1.49 - 1.6 | Not Availa |
| Corundum ( Sapphire ) | Trigonal | 9 | 4 | 1.76 - 1.7 | 0.008 |
| Danburite | Orthorhombic | 7 | 3 | 1.63 - 1.6 | 0.006 |
| Datolite | Monoclinic | 5 | 2.95 | 1.62 - 1.6 | 0.044 |
| Diamond | Cubic | 10 | 3.52 | 2.42 | None |
| Dioptase | Trigonal | 5 | 3.31 | 1.67 - 1.7 | 0.053 |
| Dravite Tourmaline | Trigonal | 7.5 | 3.06 | 1.61 - 1.6 | 0.018 |
| Dumortierite | Orthorhombic | 7 | 3.28 | 1.69 - 1.7 | 0.037 |
| Ekanite | Tetragonal | 6.25 | 3.3 | 1.57 | |
| Emerald | Hexagonal | 7.5 | 2.71 | 1.57 - 1.5 | 0.006 |
| Enstatite | Orthorhombic | 5.5 | 3.27 | 1.66 - 1.6 | 0.01 |
| Epidote | Monoclinic | 6.5 | 3.4 | 1.74 - 1.7 | 0.035 |
| Euclase | Monoclinic | 7.5 | 3.09 - 3.1 | 1.65 - 1.6 | 0.019 |
| Fire Agate | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Fluorite | Cubic | 4 | 3.18 | 1.43 | None |
| Gold | Cubic | 2.5 | 19.3 | None | None |
| Goshenite | Hexagonal | 7.5 | 2.8 | 1.58 - 1.5 | 0.008 |
| Green Tourmaline | |||||
| Grossular Garnet | Cubic | 7 | 3.49 | 1.69 - 1.7 | none |
| Hauyne | Cubic | 6 | 2.4 | 1.5 | none |
| Heliodor | Hexagonal | 7.5 | 2.8 | 1.57 - 1.5 | 0.005 |
| Hematite | Trigonal | 6.5 | 5.2 | 2.94 - 3.2 | 0.28 |
| Hessonite Garnet | Cubic | 7.25 | 3.65 | 1.73 - 1.7 | none |
| Howlite | Monoclinic | 3.5 | 2.58 | 1.58 - 1.5 | 0.022 |
| Hypersthene | Orthorhombic | 5.5 | 3.35 | 1.65 - 1.6 | 0.01 |
| Imperial Topaz | |||||
| Indicolite Tourmaline | Trigonal | 7.5 | 3.06 | 1.62 - 1.6 | 0.018 |
| Iolite | Orthorhombic | 7 | 2.63 | 1.53 - 1.5 | 0.01 |
| Ivory | Amorphous | 2.5 | 1.9 | 1.53 - 1.5 | not availa |
| Jadeite | Monoclinic | 7 | 3.33 | 1.66 - 1.6 | 0.012 |
| Jasper | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Jet | Amorphous | 2.5 | 1.33 | 1.64 - 1.6 | not availb |
| Kornerupine | Orthorhombic | 6.5 | 3.32 | 1.66 - 1.6 | 0.013 |
| Kyanite | Triclinic | 5 or | 3.68 | 1.71 - 1.7 | 0.017 |
| Labradorite | Triclinic | 6 | 2.7 | 1.56 - 1.5 | 0.01 |
| Lapis Lazuli ( Lazurite) | various | 5.5 | 2.8 | 1.5 | none |
| Lazulite | Monoclinic | 5.5 | 3.1 | 1.61 - 1.6 | 0.031 |
| Liddicoatite | |||||
| Malachite | Monoclinic | 4 | 3.8 | 1.85 | 0.025 |
| Meerschaum | Monoclinic | 2.5 | 1.5 | 1.51 - 1.5 | none |
| Microcline | Triclinic | 6 | 2.56 | 1.52 - 1.5 | 0.008 |
| Milky Quartz | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Moonstone | Monoclinic | 6 | 2.57 | 1.52 - 1.5 | 0.005 |
| Morganite | Hexagonal | 7.5 | 2.8 | 1.58 - 1.5 | 0.008 |
| Nephrite ( jade) | Monoclinic | 6.5 | 2.96 | 1.61 - 1.6 | 0.027 |
| Obsidian | Amorphous | 5 | 2.35 | 1.48 - 1.5 | none |
| Oligoclase | Triclinic | 6 | 2.64 | 1.54 - 1.5 | 0.007 |
| Paraiba Tourmaline, Copper Bearing Tourmaline | |||||
| Petalite | Monoclinic | 6 | 2.42 | 1.50 - 1.5 | 0.014 |
| Phenakite | Trigonal | 7.5 | 2.96 | 1.65 - 1.6 | 0.015 |
| Platinum | Cubic | 4 | 21.4 | none | none |
| Prehnite | Orthorhombic | 6 | 2.87 | 1.61 - 1.6 | 0.016 |
| Pyrite | Cubic | 6 | 4.9 | none | none |
| Pyro Spessartite Garnet, Color Change Garnet | |||||
| Pyrope Garnet | Cubic | 7.25 | 3.8 | 1.72 - 1.7 | none |
| Rhodochrosite | Trigonal | 4 | 3.6 | 1.60 - 1.8 | 0.22 |
| Rhodonite | Triclinic | 6 | 3.6 | 1.71 - 1.7 | 0.014 |
| Rock Crystal | Trigonal | 7 | 2.65 | 1.54 - 1.5 | 0.009 |
| Rubellite Tourmaline. Rubelite Tourmaline | Trigonal | 7.5 | 3.06 | 1.62 - 1.6 | 0.018 |
| Ruby | Trigonal | 9 | 4 | 1.76 - 1.7 | 0.008 |
| Rutile | Tetragonal | 6 | 4.25 | 2.62 - 2.9 | 0.287 |
| Sard | Trigonal | 7 | 2.61 | 1.53 - 1.5 | 0.004 |
| Scapolite | Tetragonal | 6 | 2.7 | 1.54 - 1.5 | 0.02 |
| Scheelite | Tetragonal | 5 | 6.1 | 1.92 - 1.9 | 0.017 |
| Schorl Tourmaline | Trigonal | 7.5 | 3.06 | 1.62 - 1.6 | 0.018 |
| Serpentine | Monoclinic | 5 | 2.6 | 1.55 - 1.5 | 0.001 |
| Shell | Various | 2.5 | 1.3 | 1.53 - 1.5 | not availa |
| Sillimanite | Orthorhombic | 7.5 | 3.25 | 1.66 - 1.6 | 0.019 |
| Sinhalite | Orthorhombic | 6.5 | 3.48 | 1.67 - 1.7 | 0.038 |
| Smithsonite | Triagonal | 5 | 4.35 | 1.62 - 1.8 | 0.23 |
| Sodalite | Cubic | 5.5 | 2.27 | 1.48 | none |
| Spessarite Garnet | Cubic | 7 | 4.16 | 1.79 - 1.8 | none |
| Sphalerite | Cubic | 3.5 | 4.09 | 2.36 - 2.3 | none |
| Sphene | Monoclinic | 5 | 3.53 | 1.84 - 2.0 | 0.12 |
| Spinel | cubic | 8 | 3.6 | 1.71 - 1.7 | none |
| Spodumene | Monoclinic | 7 | 3.18 | 1.66 - 1.6 | 0.015 |
| Tanzanite | Orthorhombic | 6.5 | 3.35 | 1.69 - 1.7 | 0.01 |
| Tektites | Amorphous | 5 | 2.4 | 1.48 - 1.5 | none |
| Topaz | Orthorhombic | 8 | 3.54 | 1.62 - 1.6 | 0.01 |
| Tsilisite Tourmaline | |||||
| Turquoise | Triclinic | 6 | 2.8 | 1.61 - 1.6 | 0.04 |
| Uvarovite Garnet | Cubic | 7.5 | 3.77 | 1.86 - 1.8 | none |
| Vesuvianite ( Idocrase ) | Tetragonal | 6.5 | 3.4 | 1.70 - 1.7 | 0.005 |
| Watermelon Tourmaline | Trigonal | 7.5 | 3.06 | 1.62 - 1.6 | 0.018 |
| White Topaz | |||||
| Zircon | Tetragonal | 7.5 | 4.69 | 1.93 - 1.9 | 0.059 |