June-Pearl

Colour	Usually white or pink
Formula	Variable chemical composition (may contain CaCo3)
Group	Organic
Uses	Jewellery
Origins	Created by shell fish (see below)
Locations	Red Sea, Great Barrier Reef

Pearls are very soft (2.5-3.5 on the mohs scale) and have a rainbow sheen. They are formed by oysters as a response to irrigation. When foreign bodies are present within the shell such as sand grains nacre (layers of calcium carbonate) is secreted and forms in layers around the objects. Spherical pearls tend to be the most valuable.