Since I asked the question about Melanite garnet and human behavior,
I’ll provide the answer I had in mind. (I’m on the Orchid Digest so
see posts a day later than many of the rest of you).
Melanite garnet (also known as Schorlomite) is black in color and was
used in mourning jewelry, especially in Victorian England. It is
mainly of interest to collectors today, although at one time it would
have been used in jewelry that features black “onyx” or jet now. My
source is John D. Rouse’s book, "Garnet. This association is
mentioned in many of the gem and jewelry books I’ve read, including
my old GIA course material. A significant source of this stone
exists (or used to) in Magnet Cove, AR, USA.