I,m stepping waay out of my league here,but could that be galena?I saw some once and it looked a lot like that.it came from,believe it or not,Lead Hill.Welcome to Tnet by the way.
"Pyrite and Galena are important sulfide minerals but they are different from each other in various aspects. Pyrite is iron ore while galena is lead ore. This is the main difference between them. ... The color of galena may vary from light gray to dark gray while pyrite is generally brass yellow in color."- Differencebetween.net