Diamond formation from graphite in the presence of anhydrous and hydrous magnesium sulfate at high pressures and high temperatures

The diamond forming regions in the anhydrous MgSO4 and hydrous MgSO4 . H2O- graphite systems, as well as the morphology of diamond synthesized from bot h of systems were investigated under the conditions of 6.5-7.7 GPa and 1600 -2000 degrees C. The region was basically the same in both systems, althoug h the melting point of MgSO4 is at least 600 degrees C higher than that of MgSO4 . H2O at 7.7 GPa. In the anhydrous system, the appearance of {111} fa ces is favored at higher temperatures and that of {100} faces at lower temp eratures, while in the hydrous system, {111} faces are predominant at all e xamined conditions. (C) 1999 Elsevier Science S.A. All rights reserved.