Formula: Cu5FeS4 Orthorhombic Description: Bornite forms as a primary hydrothermal precipitate or a later supergene replacement mineral. It occurs with other copper minerals such as covellite, malachite and azurite. It is marked by its intense purple to …
Winnebago County
Calcite
Formula: CaCO3 HEXAGONAL Description: Calcite sceptor crystals from Shullsburg, Wisconsin. UW–River Falls specimen. Sample is about 8 cm high. (Photo by Pete Rodewald.) Calcite is an abundant mineral found in many geological environments. It forms by precipitation from …
Celestine
Formula: SrSO4 Orthorhombic Description:Celestine forms as a groundwater or low temperature hydrothermal precipitate in sedimentary rocks such as limestones and dolostones.IRON COUNTY: Dickey (1938) describes celestine as occurring in small bluish crystals up to 0.3 mm long …
Cerussite
Formula: PbCO3 Orthorhombic Description: Cerussite is formed by the alteration of galena in the presence of carbonate. Heyl et. al. (1959) describe it as a common mineral throughout the zinc-lead district, usually as massive gray to yellowish …
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 …
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 …
Hemimorphite
Formula: Zn4Si2O7(OH)2.H2O Orthorhombic Description: Hemimorphite forms from the breakdown of sphalerite and other zinc minerals. It is common in the oxidized and supergene zones over hydrothermal deposits, where it is associated with smithsonite. Heyl et al. (1959) …