It is thought that greenockite is a seconday (supergenic) mineral, but there has been found primary greenockite in the Niujiaotang cadmium-zinc deposit in Guizhou.
When you breathe it in, it is absorbed instantly into your bloodstream, where it basically serves as a kind of chemical chauffeur for toxic compounds of cadmium to travel all around your body.
As we have seen elsewhere, our own performance with lead (not to mention mercury, cadmium, and all the other industrial pollutants with which we routinely dose ourselves) does not leave us a great deal of room for smirking.