Diamond crystals form deep within the mantle of the earth when carbon is exposed to extreme pressure and very high temperatures. Volcanic rock formations such as kimberlite or lamproite pipes serve as pathways that convey the fragments of rocks and crystals from the mantle to the surface (). The diamonds, along with vast quantities of magma, are blasted upward in the course of violent eruptions. Kimberlite pipes, the richest source of mined diamonds, are usually shaped like a carrot and can extend as deep as 1 to 2 kilometers underground. Lamproite pipes are shallower, up to kilometer in depth,.
