Pearl
Pearls have been highly valued as gemstones since antiquity, and their allure and beauty has always been magnified by the difficulty of obtaining them in early times. Unlike most other gemstones which are minerals, Pearls are organic and are formed by living organisms. They are generally formed within the soft tissue layer of mollusks such as oysters and mussels. Pearls are composed of calcium carbonate (in the form of Aragonite) and organic conchiolin that build up as concentric layers as they are secreted by their host.
| Color | White, Blue, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black, Multicolored |
| Hardness | 2.5 - 4.5 |
| Crystal System | Amorphous |
| Refractive Index | 1.52 - 1.69 |
| SG | 2.6 - 2.8 |
| Transparency | Opaque |
| Double Refraction | .156 |
| Luster | Pearly |
| Cleavage | None |
| Mineral Class | Calcium carbonate and conchiolin (organic) combined with water |
Pearls are among the most popular gemstones and have been used since antiquity. All colors and types of Pearl are used as gemstones, and they are especially popular as necklaces. Pearls are also extensively used as bracelets, and can also be the center stone in rings, earrings, and pendants. Pendants are often made of non-rounded Pearls such a baroque-shaped Pearls.
Sources:
Most Saltwater Pearl culturing takes place in the Indian and South Pacific Oceans. Pearls are primarily cultured in China, Japan, the Philippines, Indonesia, Burma (Myanmar) Australia, and in French Polynesia (especially Tahiti). Freshwater Pearls are cultured primarily in China and Japan and in several states in the U.S