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In comparison to the other precious stones and precious metals corals are not minerals, they have got an organic origin. They are coelenterates which emit calcium carbonate and this forms a skeleton, the coral. The chemical formula is CaCO3. The hardness is about 2.5 to 3. Corals are white or red. Because of their organic origin some conditions must be fulfiled that corals can grow. It is important that the water is warm. The Mediterranean and tropic areas are good for corals. To have enough coelenterates the water has to be warm. Corals are fragile and they have got a rough surface, but they change, when they are polished. When we compare raw and processed corals they are not similar to each other. In the antiquity there were made jewels of corals, too.

Data about Corals
Chemical formula CaCO3
Mineral class carbonates
Crystal system skeleton of coelenterates
Hardness 2,5 to 3
Density 2.6 g/cm3
Color white, rose, red, grey
Line color white
Gloss glass gloss
Break shell
Fissileness none

Author and Webmaster: Lukas Czarnecki

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Last Update: 03.11.2004