I once dug up an old clump of red hot poker and found a lump of a white waxy/soap like substance. I had no idea what it was. A friend suggested that it might have been a dead animal that had turned into some kind of fatty mass???
Duke
Saponification is the conversion of the fat of a corpse into adipocere, often called "grave wax." This process is more common where the amount of fatty tissue is high, the agents of decomposition are absent or only minutely present, and the burial ground is particularly alkaline.
It also occurs when you throw a corpse into a deep dark cold lake. The corpse doesnt rot, it just turns into basically a block of soap.