...Back when I attended college in New Mexico, many of my classmates were going for geo, pet eng, and mining eng degrees (ancient name for that college was The School of Mines). Some of them made an immodest income by highgrading from the many local mines at night and selling to the many local rock shops by day. I went on a couple of these expeditions just for the fun and danger of it (Kelly mine and Nancy mine).
Now here's the question: from the Nancy mine, one frequent haul was a black mineral that had a thick black velvet-like fur. If you touched the fur it smashed down and turned into a black smear on your fingers and on the rock base (and disappeared from the rock base - it was very fragile stuff). The resulting smear was not quite as soft as graphite and it was more of a flat black than a shiny one. What's the mineral?