From Lost Fables Wiki
Stonemold is a crystalline growth which grows on veins of ore deep underground. The mold itself is very visually uninteresting, looking like gray, stony mold, thus its name. Its texture is hard and brittle on the outside, though it is a bit softer on the inside. Eating it raw is supposedly good for skin and hair.
Gathering stone mold is just as easy as finding it. Any person could scrape the mold from the wall with a fingernail, and it can be carried in any way the person gathering it so chooses. Unfortunately, growing it is almost impossible, for a reason nobody quite knows.
Stonemold can be used in a great variety of alchemical mixtures, and when it is used as a base ingredient, it turns almost anything used afterwards into a protective product. A basic potion using only it toughens the skin and constitution of the subject.