My off the top guess was an oxide of some sort. Or bornite. It's dark enough, and soft enough, and would not be unexpected in the district. But the crystal habit isn't quite right. Did it have a tarnish?

psilomelane A bit harder than you describe. Was it black, or really dark green? Don't suppose you dropped acid. On the mineral, I mean, to test for carbonate.

Here's a list of minerals from the Kelly Mine:
http://www.mindat.org/loc-3986.html.