On the Origin of Natural Diamonds.

Abstract

So far, not all the different kinds of diamonds found in nature can be duplicated by men, but enough laboratory experience in diamond formation has been accumulated to make possible the comparison of several kinds of natural and man-made diamonds In this way some tentative hypothesis can be made about the origin of natural diamonds, both meteoritic and terrestrial. It is proposed that most natural diamonds were formed at high pressures and temperatures in the presence of an iron-alloy catalyst. The black polycrystalline meteoritic diamonds could have been formed at low temperatures (1200 C) and high pressures (above 55000 bars). The larger terrestrial crystals could have formed at somewhat higher temperatures and pressures by a falling-temperature and/or increasing-pressure process.