Certain races should be able to forge using materials other races can’t:

• Dwarves can forge with crystal items, and possibly stone.
• Orcs can forge with stone items. Bone would be more flavorful for orcs, but less flavorful in being something that can actually be forged with.

Since stone golems don’t actually drop anything except a statue of themselves upon death, clay golems should drop random items made of stone when they are killed, similar to how golems of other materials do.