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 …
Lafayette County
Gold
Formula: Au Isometric Description:Gold is usually found in hydrothermal deposits where it forms at a wide range of temperatures and geological settings. Gold may form in exhalative deposits formed on the sea floor associated with Archean …
Goslarite
Formula: ZnSO4.7H2O Orthorhombic Description: Goslarite is an alteration product of sphalerite and other zinc minerals. It is water soluble and dehydrates readily under surface conditions, hence, although it may frequently form, it is only rare found …
Greenockite
Formula: CdS Hexagonal Description: Greenockite is a bright yellow mineral formed by hydrothermal fluids. In Wisconsin it is rarely found associated with sphalerite in the deposits of the Upper Mississippi Valley zinc-lead district. GRANT COUNTY: Occurs at …
Gypsum
Formula: CaSO4.2H2O Monoclinic Description: Gypsum is a relatively common mineral in a number of environments. It is found in sedimentary rocks, either as a primary precipitate from sea or saline lake waters or as a alteration …
Hematite
Formula: Fe2O3 Hexagonal Description: “Needle Ore” hematite, longest needle is about 20 cm long. From Montreal Mine in Iron County, Wisconsin. (Image courtesy W. S. Cordua.) Hematite is an extremely common mineral. It can form as a …
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) …
Honessite
Formula: Ni6Fe2(SO4)(OH)16.4H2O Hexagonal Description: Honessite is one of a number of secondary nickel sulphates formed by the weathering of primary hydrothermal nickel sulfides such as millerite, violarite or nickeliferous pyrite (so-called “Bravoite”). It is found at …
Hydrocarbons
Formula: Mixtures Description: Solid hydrocarbons, generally unanalyzed in detail, are found at a number of localities within the Paleozoic rocks around the state. They may be alternately described as “bitumen” or “asphaltum”. These usually occur as …
Hydrozincite
Formula: Zn5(CO3)2(OH)6 Monoclinic Description: Hydrozincite forms white earthy massive to reniform to stalactitic growths due to the alteration of sphalerite and other zinc minerals by ground water. It is likely quite common (but not often reported) in …