To help narrow your search, you might want to check it's "hardness" with a glass plate and also do a "streak" with a streak plate. I think these plates can be purchased probably at a hobby store and there really cheap.
Here's a few choices:
METALLIC:
HARDER THAN GLASS:
STREAK NAME
----------------- ------------------------
black Magnetite
greenish-black Pyrite (fools gold)
red-brown Hematite
SOFTER THAN GLASS:
gray-black (silvery black) Galena
These are not all but just a few that I remember. Also, I believe Galena had a greenish tint if I remember correctly.
Hope this helps
Fatstrings
"I'm not going to buy my kids an encyclopedia. Let them walk to school like I did." Yogi Berra
"It's like deja vu all over again." Yogi Berra
and my personal favorite Yogi Berra quote: "Ninety percent of this game is half mental."