11. Chalcopyrite is rarely found in association with native copper . 12. Other minerals noted within the ore bodies are willemite, sphalerite, chalcopyrite and rare native copper . 13. Halite stalactites and encrustations are also reported in the Quincy native copper mine of Hancock, Michigan. 14. Isle Royale in western Lake Superior was also a site of many tons of native copper . 15. It appears at this occurrence, dioptase is primary and has crystallized with quartz, native copper , and malachite. 16. Often, the nature of the gangue is important, as clay-rich native copper ores prove difficult to liberate. 17. The principal ore mineral was chalcocite, although native copper predominated in the lower part of the beds. 18. Polished native copper nugget from Keweenaw County. 19. The same deposits of native copper on the Keweenaw Peninsula and Isle Royale were later mined commercially. 20. The main ore exploited in those times was native copper from the oxidation zone of the deposit.
