CHARACTERISTICS OF SOME COMMON GEMS
| Approximate average of | ||||||
|---|---|---|---|---|---|---|
| (1) hardness | ||||||
| (2) specific gravity | (4) Dispersion | |||||
| (3) refractive index | (5) Durability | |||||
| Species | (1) | (2) | (3) | (4) | (5) | Usual color range |
| Beryl | 7¾ | 2.70 | 1.58 | Low | High | Green (emerald), blue-green (aquamarine), pink (morganite), colorless (goshenite) |
| Chrysoberyl | 8½ | 3.71 | 1.75 | Low | High | Yellow, green, brown |
| Corundum | 9 | 4.00 | 1.77 | Low | High | Red (ruby), various (sapphire) |
| Diamond | 10 | 3.52 | 2.42 | High | High | Colorless |
| Garnet group | 7½ | 3.70-4.16 | 1.74-1.89 | Medium to high | High | Yellow, red, green, brown |
| Jade (nephrite) | 6½ | 2.96 | 1.62 | None | High | Green, white |
| Jade (jadeite) | 7 | 3.33 | 1.66 | None | High | Green, white |
| Opal | 6 | 2.10 | 1.45 | None | Low | Red, dark gray, orange, white, with or without varicolored fire |
| Pearl | 3½ | 2.71 | None | None | Low | White |
| Peridot | 6½ | 3.34 | 1.68 | Low | Medium | Yellow-green, brownish green |
| Quartz | 7 | 2.65 | 1.55 | Low | High | Purple (amethyst), yellow (citrine), colorless (rock crystal) |
| Spinel | 8 | 3.60 | 1.72 | Low | High | Shades of red, green, blue, violet |
| Spodumene | 7 | 3.18 | 1.66 | Low | Low | Colorless, pink, yellow, green |
| Topaz | 8 | 3.54 | 1.63 | Low | Medium | Colorless, sherry, pink, blue |
| Tourmaline | 7 | 3.06 | 1.63 | Low | High | Wide range, except bright red |
| Zircon | 7 | 4.02 | 1.81 | High | High | Almost colorless, blue, brown, green, yellow |