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 …
Lafayette County
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 …
Chalcocite
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 …
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, …
Cobaltite
Formula: CoAsS Orthorhombic Description: Cobaltite is a rare mineral found as silvery metallic grains in hydrothermal deposits. When present in sufficient quantities, it is used as an ore of cobalt. LAFAYETTE COUNTY: Cobaltite (or possibly safflorite -CoAs2) …
Copper
Formula: Cu Isometric Description: Native copper occurs as veins and cavity fillings in hydrothermally altered basaltic igneous rocks. It is also a product of near-surface supergene alteration of other copper minerals, such as chalcopyrite. Copper can …
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 …
Epsomite
Formula: MgSO4.7H2O Orthorhombic Description: Epsomite usually forms as powdery, fibrous or botryoidal crusts growing as efflorescences on magnesium-rich rocks or as deposits around mineral springs. It is highly water soluble, hence will not survive long under …
Erythrite
Formula: Co3(AsO4)2.8H20 Monoclinic Description: Erythrite is a pink to purple powdery to acicular mineral formed as a result of near-surface alteration of other cobalt-rich minerals. LAFAYETTE COUNTY: Erythrite was tentatively reported as intermixed with melanterite as an …