What does moldy marijuana look like?

Not if it's just the fuzzy, greyish-white kind of mold (although, you should try to pick as much of the mold off as you can before smoking). If it's a thick, black mold, then you should throw it away.

It is unsafe to smoke any kind of mold. There is a new company that offers testing of medical marijuana's. They test for pesticides, mold, and other harmful substances. They also list some of the metabolites by percent.