NASA researchers have detected large numbers of nanodiamonds in some meteorites. (Nanodiamonds are diamonds that are a few nanometers – billionths of a meter in diameter.) About three percent of the carbon in these meteorites is contained in the form of nanodiamonds. These diamonds are too small for use as gems or industrial abrasives; however, they are a source of diamond material. See Location 4 in the diagram at the top of the page.

Smithsonian researchers also found large numbers of tiny diamonds when they were cutting a sample from the Allen Hills meteorite. These diamonds in meteorites are thought to have formed in space through high-speed collisions similar to how diamonds form on Earth at impact sites.

Is coal involved? Coal is not involved in the creation of these diamonds. The carbon source is from a body other than Earth.