Copper pyrites (or yellow ore), erubescite (or purple ore), and chalcocite (or grey ore) are the most important.
In the United Verde Mine, oxidizing conditions at present prevail to the bottom of the chalcocite zone.
No traces of other primary minerals are present and the chalcocite here is regarded as probably primary.
chalcocite occurs in vein deposits as one of the important copper ores, especially at Butte, Montana.
The mineral is harder than chalcocite, but less hard than pyrite, being easily scratched with a knife.
The streak will serve to identify any specimen, however, it being a lead-gray of much lighter shade than that of chalcocite.