Consisting largely of carbonate minerals, carbonatite is essentially an igneous limestone. They form short, vertical veins (volcanic plugs) in igneous rock. Like pegmatites, carbonatite veins are enriched for valuable minerals, in particular rare earths and niobium minerals. Besides carbonatite itself, the veins have the following composition:

Ore/Mineral Percent
Bastnasite 5%
Apatite 5%
Vermiculite 4%
Chalcopyrite 2.5%
Barite 2.5%