Calamine

According to Wikipedia (and dictionary.com agrees), calamine is "a combination of zinc oxide and 0.5% ferric oxide (Fe2O3)."

Wikipedia does say, further down the same page, that calamine is "mixed with either zinc oxide (ZnO) with about 0.5% ferric oxide (Fe2O3) or a zinc carbonate compound."

I'm not at all sure what this means!