An igneous rock in which carbonate minerals make up at least half the volume. Individual occurrences of carbonatite are not numerous (about 330 have been recognized) and generally are small, but they are widely distributed. Carbonatites are scientifically important because they reveal clues concerning the composition and thermal history of the Earth's mantle. Economically, carbonatites provide important mines for some mineral commodities and are virtually the only sources of a few.