Pearl is a mixture of mineral and organic material formed with the soft living tissue of a shelled mollusk. Chemically pearls are made of calcium carbonate (mainly aragonite or a mixture of aragonite and calcite).
Pearls have been used for adornment for 6,000 years. Pearls do not require any processing because they show full gloss and attractive lustre in their natural state.
Specific gravity for natural and Oriental pearls = 2.68-2.74; for cultured pearls = 2.70-2.79; and for freshwater pearls = 2.68.
Texture: slightly rough.
Luster: pearly (iridescent)
Color: white, pale yellow, pink, gray, brown, black.