In 1981, geologist John Saul wrote what may be a classic paper on diamonds and deep gas, which we now post to our site. The full reference is: John M. Saul, The Origin of Diamonds and the Deep Gas Hypothesis, Proceedings of the XVIII International Gemmological Conference, Journal of the Gemmological Society of Japan, Vol.8, no1-4 (Dec. 1981) pp.79-85.