Dave, orpiment is very soft - Mohs1.5 - 2. I'm having trouble understanding how it could be cabbed & polished unless it is as inclusions in a much harder material. If this is the case, maybe the orpiment is unavailable to the touch and MAY be safe.....I wouldn't wear it!!
I was curious about this also, I have some banded orpiment cabachons which the host matrix is noted as calcite, still pretty soft. I purchased them for collection rather than jewellery, so it won't be worn anyway, but I would still like to know.