Formula: Mixture Description: Ferromanganese nodules similar to those found on the deep sea floor occur in several lakes in Wisconsin, including Lake Michigan. They consist of a mixture of manganese oxides, iron oxides, sand and clay. …
Oneida County
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 …
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 …
Grossular
Formula: Ca3Al2(SiO4)3. Isometric Description: Grossular is a member of the garnet family found as pale white, green or tan crystals, most often in marbles, calc-silicate and other metamorphic rocks formed from calcium rich protoliths. MARATHON COUNTY: Small …
Hydromagnesite
Formula: Mg5(CO3)4(OH)2.4H2O Monoclinic Description: Hydromagnesite forms white chalky masses or, occasionally sprays of radiating acicular to bladed crystals due to the alteration and weathering of magnesium-rich rocks. CRAWFORD COUNTY: Hydromagnesite is a major component of moon-milk …
Magnetite
Formula: Fe2+Fe3+2O4 Isometric Description: Magnetite is a common mineral found at many localities in Wisconsin. Only localities that where the mineral is present in great abundance or as unusual material are listed here. Magnetite occurs as an …
Phlogopite
Formula: KMg3(AlSi3O10)(OH)2 Monoclinic Description: Phlogopite is a tan mica found most often in magnesium-rich rocks such as marbles, calc-silicate and ultramafic rocks. KENOSHA COUNTY: Phlogopite occurs in a subsurface, diamond-bearing lamprophyre diatreme, discovered within the outskirts of Kenosha …
Pyrargyrite
Formula: Ag3SbS3 Hexagonal Description: Pyrargyrite is a deep red to nearly black mineral found in hydrothermal veins often associated with other silver minerals, galena, pyrite and quartz. ONEIDA COUNTY: Pyrargyrite occurs at the Lynn massive sulfide deposit, in …
Pyrite
Pyrite is the most common sulfide found in many environments. It is a common accessory mineral in igneous, sedimentary and metamorphic rocks. It also is abundant in most hydrothermal deposits. Only the most significant occurrences …
Pyrrhotite
Formula: Fe1-xS Monoclinic Description: Pyrrhotite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 867. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by …