The search for diamonds has determined that most are derived from kimberlite pipes in the oldest, nuclear portions of the continents, where the basement rocks are older than 1.5 billion years.

The oldest parts of continents are called cratons, and can be divided into two terranes: Archean-age archons, which are older than 2,500 million years, and Proterozoic-age protons, which are 1,600 -- 2,500 million years old. The distribution of these terranes is shown on the map. Kimberlite pipes occur in many parts of the continental crust, but most diamond-rich ones are found in archons. This fact suggests that most diamonds were formed and stored deep below the cratons, in the area shown in the lower figure, and were later transported to the surface by kimberlite and lamproite magmas that extracted them and other samples from the mantle.