It doesn't sound very interesting or lovely, but it is, because zaffer can be used to prepare smalt, which is the stuff that makes glass blue:
photo by Arpingstone
Zaffer has also been used in blue enamel and, in the form of a glaze, on blue and white pottery.
Jingdezhen vase, about 1415. Photo by World Imaging,
So much beauty from a lump of contaminated rock.
Zaffer used to be used in alchemy.
I think it's of the discipline's great successes, too.