Rearrangement product of steranes during diagenesis. The rearrangement involves migration of C-10 and C-13 methyl groups to C-5 and C-14 and is favored by acidic conditions, clay catalysis, and/or high temperatures. Diasteranes increase in abundance with increasing thermal maturity, thus the Diasterane / Sterane ratio may be a signal of the maturity of the source rock. They are also in high abundance in source rocks and oil associated with clastic environments (e.g. clays or shales).