Bill: These three copper sulfides were all prominent in the Butte ore deposits, but they are not easy to tell apart in hand sample.....digenite tends to be dark gray and has a fairly good, almost pitchy luster on a freshly broken surface, plus the fracture is similar to quartz. Chalcocite tends to be dull gray with a dull luster, earthy fracture and often exhibits a "sooty" coating upon exposure....rubbing the sample should yield a black powder. Djurleite often goes unrecognized for what it is; it is colored a more silvery hue and has a submetallic luster. Unless you have reasonable crystals of these minerals, they are tough to distinguish, but digenite is the most easily recognized.

Thanks for the good input. I can see it's a tough problem. Appreciate the help!