Natural Pearl
| Category |
| Organic |
| Crystal Form |
| Orthorhombic |
| Moh's Scale Hardness |
| 2.50–4.50 |
| Specific Gravity |
| 2.68–2.74 |
| Refractive Index |
| 1.53–1.68 |
Natural pearl are pearls without any human intervention. It is made out of 100% nacre.
How do pearls form?
Pearls are produced by a living organism, called mollusks such as oysters. Pearls are composed of a substance that is identical with its shells or the mother-of-pearl, known as nacre. Mollusk that possesses a nacreous shell can produce pearl.
Pearl is produced as a response to an intruder settled inside the oyster. Foreign object, such as sand, entered between the shell and the mantle of the oyster. To crease irritation caused by the intrusion of foreign object, the mollusk will secrete layers of nacre. The mollusk would repeat the process over a period of time and a pearl is formed.
Nacre produced by the mollusk consist the combination of calcium carbonate (CaCO3) in the form of aragonite and an organic horn-like compound called conchiolin. The alternating layers of aragonite and conchiolin on the surface produce the orient of the pearls.