Definition
A Carbonatite is a rare type of igneous rock (volcanic) composed of greater than 50% carbonate minerals. It is effectively “volcanic limestone.”
Significance
They are the “Elephants” of the rare earth world. The biggest and best mines—Bayan Obo, Mountain Pass, and Mount Weld—are all hosted in Carbonatite pipes. If a geologist finds a Carbonatite, they get very excited.