Formula: Cu3(CO3)2(OH)2 Monoclinic
Description: Azurite is an attractive blue mineral found as a secondary weathering and supergene mineral formed from the alteration of native copper and other copper minerals. It is often found associated with and altering too malachite, but is considerable less common than this mineral. Other commonly associated minerals include chalcocite, chalcopyrite, cuprite, tenorite, calcite, and goethite. Most of the azurite occurrences in Wisconsin are from the more copper-rich deposits associated with the zinc-lead ares in southwestern Wisconsin, notable Iowa and Crawford Counties.
BAYFIELD COUNTY: With copper sulfides and malachite in test pits NW NW Sec. 6 T.44N. R.5W. north of Namekagon Lake (Dutton, 1972).
— With copper sulfide and malachite in prospect pits NE NW Sec. 2 T.44N. R6W., north of Namekagon Lake (Dutton, 1972).
— With copper sulfides and malachite in prospect pits NE SE Sec. 15 T.44N. R.9W. near Upper Eau Claire Lake (Dutton, 1972).
CRAWFORD COUNTY: Found with malachite at old Copper Creek Mine, W 1/2 Sec. 26 T.10N. R.5E. 1 km west of Mt. Sterling (Heyl et al., 1959).
— Found with chalcocite and malachite as an alteration product of chalcopyrite at the old Plum Creek Copper Mine, (SE 1/4 SW 1/4 Sec. 26 T.8N. R.5W.) approximately 8 km. northwest of Wauzeka along Otter Creek (Heyl et al., 1959).
IOWA COUNTY: Azurite was widely known in attractive drusy crystals specimens from some of the more copper-rich deposits of the Mineral Point region, as noted by Irving (1883) and Raasch (1924). Hobbs (1905) described the crystals in some detail, noting that they may be 4 mm.long, though more commonly they are 2 mm or less in length. The crystals have complex tabular habit, a deep blue color, and, occasionally, thin coatings of malachite. The azurite occurs with tenorite and limonite as alteration products of chalcopyrite. Some specific localities from the Mineral Point area given by Heyl et al. (1959) are the Beach Copper Mine (S 1/2 Sec. 4 T.4N. R.3E.), the Wasley Copper mine (N 1/2 SE 1/4 NW 1/4 Sec. 5 T.4N. R.3E), and the Ansley Copper Mine (N1/2 SE 1/4 Sec. 32 T.5N. R.3E.). At the Ansley Mine, the copper minerals occur as masses weighing up to 200 lb in clay.
—Found at the Eberle Mine, 5 miles north of Cobb at NW 1/4 NW 1/4 Sec. 2 T.6N. R.1E. where it is associated with malachite, chalcocite, chrysocolla, aurichalcite, sphalerite and smithsonite (Heyl et al., 1959).
— Found at the Steppler Farm, 4 miles southwest of Highland in SE 1/4 NE 1/4 Sec. 7 T.6N R.1E where it is associated with malachite, chrysocolla, chalcocite, chalcopyrite, sphalerite, smithsonite and aurichalcite (Heyl et al., 1959).
LAFAYETTE COUNTY: Reported as crusts and films on dolostone and in goethite at copper prospects south of Ames Branch in the NE 1/4 SE 1/4 Sec. 22 T.2N. R.3E. of the Calamine Quadrangle (Klemic and West,1964).
— Found with malachite, cuprite, tenorite, pyrolusite, wad, native copper, bornite, chalcopyrite, and chalcocite 4 miles northwest of Gratiot in the SE 1/4 NW 1/4 Sec. 36 T.2N. R.3E (Heyl et al., 1959).
RUSK COUNTY: Found as massive to drusy crusts and botryoidal masses in the gossan zone overlying the Flambeau massive sulfide deposit south of Ladysmith. Some crystal cluster form rosettes up to 2 cm. across associated with malachite, cuprite, tenorite and native copper (May, 1977; Rosemeyer, 1995 and 1997).
WOOD COUNTY: Rare, as crusts with malachite on serpentine and soapstone at the talc mines at Milladore (W.S.Cordua, field notes).