Formula: Cu2S Monoclinic Description: Chalcocite is formed either as a primary vein mineral or, more typically, in supergene deposits where it forms as a result of the redeposition of copper from the breakdown of minerals such …
Iowa County
Chalcopyrite
Formula: CuFeS2 Tetragonal Description: Chalcopyrite is an important ore of copper found in a wide range of hydrothermal environments. It is often associated with sphalerite and galena. It oxidizes to form copper minerals such as malachite, azurite, …
Chrysocolla
Formula: (Cu,Al)2H2Si2O5(OH)4.nH2O Monoclinic Description: Chrysocolla is a blue copper-rich clay mineral that forms as an alteration product of other copper minerals in supergene and oxidized zones. IOWA COUNTY: Reported at the Steppler Farm, 4 miles SW of …
Covellite
Formula: CuS Hexagonal Description: Covellite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 430. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by …
Cuprite
Formula: Cu2O Isometric Description: Cuprite, Flambeau Mine, Rusk County, WI. Fibrous chalcotrichite. Vertical field of view is about 0.3 mm. (Image courtesy Dan Behnke, specimen collected by Dan Behnke.) Cuprite generally forms from the alteration of …
Dolomite
Formula: CaMg(CO3)2 Hexagonal Description: Dolomite forms the main mineral in the bluff-forming rocks along the Mississippi River, such as Granddad Bluff near La Crosse. (Image courtesy W. S. Cordua.) Dolomite is an abundant mineral in Wisconsin. It …
Enargite
Formula: Cu3AsS4 Orthorhombic Description: Enargite is a rare hydrothermal mineral found associated with other copper minerals. FOREST COUNTY: Small grains of enargite occur with bornite and digenite replacing chalcopyrite at the Crandon deposit near Little Sand Lake. (Lambe …
Fluorite
Formula: CaF2 Isometric Description: Fluorite crystals, from Sturgeon Bay in Door County, Wisconsin. Field of view is about 4 cm. (Image courtesy W. S. Cordua.) Fluorite often forms coarse cleavable masses or cubic crystals. It can take …
Galena
Formula: PbS Isometric Description: Galena crystals surrounded by marcasite, from Shullsburg, Wisconsin. (Image courtesy W. S. Cordua.) Galena is formed in a wide range of hydrothermal environments. It can be found with sphalerite and chalcopyrite in …
Glauconite
Formula: (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2 Monoclinic Description: Glauconite is abundant in the Paleozoic sandstones in Wisconsin where it forms rounded dark green sand-sized nodules. At places glauconite may make up the majority of the rock, forming what are commonly called …