Gemstone Properties: The Collector's Interactive Reference
Gemstone Properties, Physical Characteristics & Optical Data
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Click on any column header to sort the table. Click on a gemstone name to view its collection on Skyjems.
| Gemstone Material ▲▼ | Refractive Index (RI) ▲▼ | Specific Gravity (SG) ▲▼ | Hardness (Mohs) ▲▼ | Birefringence ▲▼ | Optic Character / Additional Data ▲▼ |
|---|---|---|---|---|---|
| Alexandrite (Chrysoberyl) | 1.741 - 1.757 | 3.70 - 3.74 | 8.5 | 0.008 - 0.015 | Biaxial |
| Axinite | 1.668 - 1.680 | 3.20 | 5 - 5.5 | 0.012 | Strong pleochroism |
| Cubic Zirconia (Synthetic) | 2.150 - 2.180 | 5.56 - 6.00 | 8 - 8.5 | None | Singly refractive (Isotropic); Dispersion: 0.058-0.066 |
| Diamond | 2.417 | 3.52 | 10 | None | Singly refractive (Isotropic); Dispersion: 0.044 |
| Diaspore | 1.700 - 1.750 | 3.3 - 3.5 | 6.5 - 7 | 0.048 - 0.049 | Biaxial positive; Orthorhombic |
| Emerald (Beryl) | 1.564 - 1.602 | 2.6 - 2.9 | 7.5 - 8 | 0.005 - 0.010 | Uniaxial negative; Hexagonal |
| Garnet: Andradite (Demantoid) | 1.880 - 1.889 | 3.77 - 3.88 | 6.5 | None | Singly refractive (Isotropic); Dispersion: 0.057 |
| Garnet: Grossular (Tsavorite) | 1.731 - 1.760 | 3.40 - 3.78 | 7 | None | Singly refractive (Isotropic); Dispersion: 0.028 |
| Garnet: Uvarovite | 1.798 - 1.868 | 3.71 - 3.81 | 7.5 | None | Singly refractive (Isotropic) |
| Grandidierite | 1.580 - 1.633 | 2.96 | - | 0.039 | Biaxial negative; Pleochroic |
| Hackmanite (Sodalite) | 1.45 - 1.47 | 2.28 - 2.30 | 5.5 - 6 | - | Tenebrescent properties |
| Hemimorphite | 1.61 - 1.63 | 3.45 | < 5 | 0.02 | Hydrated zinc silicate |
| Herderite | 1.578 - 1.611 | 3.04 | 5 - 5.5 | 0.029 - 0.031 | Strong doubling under magnification |
| Hibonite | 1.79 - 1.81 | 3.84 | 7.5 - 8 | - | Inert to long/short-wave UV |
| Jadeite | 1.65 - 1.67 | 3.31 - 3.34 | 6.5 - 7 | - | Interlocking granular structure; Pyroxene |
| Jeremejevite | 1.640 - 1.651 | 3.27 - 3.31 | - | 0.009 | Uniaxial negative (sometimes biaxial core/rim) |
| Natrolite | 1.49 (spot) | 2.24 | 4.4 - 4.6 | - | Polycrystalline |
| Nephrite | 1.600 - 1.641 | 2.90 - 3.02 | 6 - 6.5 | - | Interwoven fibrous structure; Amphibole |
| Oligoclase (Feldspar) | 1.531 - 1.543 | 2.63 - 2.65 | 6 | 0.010 - 0.012 | Biaxial positive/negative |
| Pectolite | 1.59 - 1.63 | 2.62 - 2.90 | 4.5 - 6 | - | Polycrystalline |
| Peridot | 1.653 - 1.689 | 3.36 | 6.5 - 7 | 0.036 | Biaxial positive |
| Rhodizite-Londonite | 1.689 - 1.693 | 3.34 - 3.42 | 8 | None | Singly refractive (Isotropic/Isometric) |
| Ruby & Sapphire (Corundum) | 1.760 - 1.776 | 3.94 - 4.03 | 9 | 0.008 - 0.010 | Doubly refractive (Uniaxial negative) |
| Sapphirine | 1.701 - 1.711 | 3.49 - 3.50 | - | 0.007 | Strong pleochroism |
| Sepiolite (Meerschaum) | 1.506 - 1.529 | 2.0 | 2 - 2.5 | 0.009 - 0.019 | Floats on water |
| Serendibite | 1.696 - 1.702 | 3.43 - 3.44 | - | 0.005 | Biaxial negative; Strong pleochroism |
| Spinel | 1.714 - 1.753 | 3.58 - 4.05 | 8 | None | Singly refractive (Isotropic) |
| Spodumene | 1.659 - 1.677 | 3.20 | 6.5 - 7 | - | Pleochroic |
| Synthetic Moissanite | 2.648 - 2.691 | 3.22 | 9.25 | 0.043 | Doubly refractive (Uniaxial positive); Dispersion: 0.104 |
| Taaffeite | 1.716 - 1.728 | 3.61 - 3.67 | ~8 | 0.004 - 0.006 | - |
| Topaz | 1.610 - 1.620 | 3.56 | 8 | 0.010 | Biaxial positive |
| Tourmaline | 1.618 - 1.645 | 3.05 - 3.20 | - | 0.016 - 0.023 | Uniaxial negative |
| Zircon | 1.925 - 1.984 | 4.62 - 4.72 | - | 0.038 - 0.059 | Uniaxial positive; Dispersion: 0.038 |
Watch the Video Series
Three short films on the measurements that separate connoisseurship from guesswork.
I · Five Numbers That Tell You Everything
II · Mohs Hardness
III · What is Birefringence?
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