What It Actually Is

Orpiment is identified as arsenic trisulfide, As2S3, an identification well confirmed by modern mineralogical analysis and consistent with every historical description of its color, luster and occurrence alongside realgar. There is no meaningful scholarly dispute over the compound's modern chemical identity; the more interesting historical point is the mismatch between the alchemical theory that made orpiment attractive, its resemblance to gold as grounds for investigating a hidden kinship between the two, and the modern chemical reality, that arsenic and gold share no meaningful chemical relationship beyond a coincidence of visual color that has nothing to do with either element's actual reactivity or atomic structure. This is a clear case where an alchemical hypothesis, tested with real experimental effort over centuries, was not confirmed by later chemistry, and the historical record of orpiment's use in failed transmutation attempts is itself a useful, honestly negative data point about how alchemical reasoning from surface resemblance could lead investigators toward substances that were, in the end, chemically unrelated to their goal. Modern toxicology adds a further, sobering note absent from most historical accounts: prolonged exposure to orpiment as a working pigment carried real health risk for painters and manuscript illuminators, a hazard largely undocumented at the time but now well understood.