"I have some beautiful crystals... these green ones and the blue ones... have been observed... [from] water evaporating on the side of lakes... close to volcanoes... [T]hey have... a glassy appearance. ...[T]he Sumerians, 2000 years ago ...described these ...The Latin word for glass is vitriolus [or vitrum] and so glassy substance became known as vitriols. ...[T]he medieval chemists discovered that if you heat these [crystals] very strongly... they give off a... terribly powerful smell and... a liquid which is capable of dissolving... metals. ...It was called oil of vitriol because it came from those glassy substances, but today we call it ."