I ran a quick search on black gold (www.gold.org) but failed to come up with anything. I know I've seen a technical article on black gold somewhere (I was an avid collector of colored gold alloys), but can't locate it. Perhaps I was dreaming? Will keep looking....
The technical article seems to be gone. I posted it a long time ago
to the list:
(10 minutes later)
So with a bit of monkeying around with their new reorganization,
here it is: