"There are many other sulfides, but this one is... special... Known in the ancient world as dragon's blood, and the reason... this red color. ...[W]hen they heated this strongly ...(This was particularly well known in ancient China and... in southern Spain.) ...it makes two... remarkable substances. One of them is sulfur... the other... is the liquid metal... mercury. ...[T]his fired up the imagination of ...ancient philosophers ...asking questions about ultimately what are all s made of."