why black? cause there is black iron (a form of iron that has a black finish, and iron that is more 'silvery" in tone..(that oxidizes almost immediately! a thin even oxidation layer actually works to protect from more corrosive rust..

think of iron pots.. black 'cast iron', and silvery pots (which is really an iron alloy--(steel is one alloy, but there are others)
a black smith works in black iron.

lots of pots had tin linings (to keep the iron from rusting) and some had pots of copper (much more expensive than iron) that also had tin linings.

(brass also comes in 'yellow brass" and "red brass", gold in pink, white and yellow, lots of metals were 'defined' by color.

my other obsession