Abstract: The synthesis of diamonds from salts of iron, manganese, calcium and magnesium is disclosed. Specifically, such synthesis, in a closed system, has involved carbonate and oxylate salts of the indicated metals. The reaction occurs at temperatures between 550.degree. and 1600.degree. C., higher temperatures requiring higher reaction pressures; specifically, the production of synthetic diamonds from ferrous carbonate is disclosed. The ferrous carbonate was packed into a platinum capsule which was sealed gas-tight, packed in unfired pyrophyllite, and heated for two hours at 900.degree. C. while in a solid media press which applied a pressure of 40 kb (subsequently defined).