https://www.cnbc.com/2018/07/18/quadrillion-tons-of-diamond-may-be-buried-100-miles-under-earth.html

There might be a quadrillion tons of diamond hiding deep underneath Earth's surface, according to a new study. But it will be a while until diamonds are every girl's best friend: the lavish gems are located so deep, no drill in existence can reach them.

Located over 100 miles below Earth's tectonic plates are ancient, hard rocks called "cratonic roots" that potentially consist of one to two percent diamond — totaling a quadrillion tons. Researchers at Massachusetts Institute of Technology and other universities studied sound waves that rumble through Earth's surface after a natural disaster or explosion, called seismic data, to uncover the type of rocks concealed beneath.