126-175 Carbonates

In nature, carbon atoms join with oxygen to form the carbonate ion, CO3. These ions combine with metal ions to form carbonate minerals. Generally, the carbonate minerals are found at or near the Earth's surface. They represent the Earth's largest storehouse of carbon.

The carbonates fall into three groups: the calcite group, the dolomite group, and the aragonite group, with the difference being in their crystal structures. The copper carbonate minerals, azurite and malachite, are important economic carbonates and together indicate the presence of a copper ore.

Minerals of the carbonate class are transparent, lightly-coloured with a white streak, have average to above average specific gravity, are soft with good to perfect cleavage, and are soluble in acidic solutions.

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