The main composition of carbonatite is calcite which have an igneous origin. Carbonatite is an intrusive or extrusive rock which sometimes is confused with marble. It consists more that 50% carbonate minerals and less than 10% SO2. On the earth there is only 330 carbonatite localities, most of them being shallow intrusive bodies of igneous rocks rich in calcite. Only one volcano of carbonatite has erupted so far. It is the Ol Doinyo Lengai volcano in Tanzania. Carbonatite is usually not sold for commercial purpose.