Formula: Mixture of pyrophillite and sericite. Description:Pipestone is a compact pink to red metamorphosed mudstone (or argillite) of a consistency that allows it to be carved into pipes and other art objects. It is found as thin …
Sawyer County
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 …
Potassium Feldspar
Formula: KAlSi3O8 Monoclinic or Triclinic Description: Potassium feldspar refers to any of the three polymorphs microcline, orthoclase or sanidine. The distinction between these minerals can be made with certainty only after detailed X-Ray analysis. This has not …
Pyrophyllite
Formula: Al2Si4O10(OH)2 Monoclinic Description: Pyrophyllite is a micaceous mineral formed as a result of the relatively low grade metamorphism of aluminum-rich rocks. It can also form as a hydrothermal replacement of aluminous minerals such as feldspars. The …
Biotite Group
Formula: K(Mg,Fe)3(Al,Fe3+)Si3O10(OH,F)2 Monoclinic Description: Biotite refers to a group of common rock-forming minerals forming a series between phlogopite and annite. The name is best used as a field name for dark micas for which the exact composition …
Kyanite
Formula: Al2SiO5 Triclinic Description: Kyanite schist outcrop near Powell in Iron County, Wisconsin. (Photo courtesy Tod Roush.) Kyanite is formed by the metamorphism of aluminum-rich rocks, and is often associated with biotite, muscovite, almandine, staurolite, and sillimanite. It …
Quartz
Formula: SiO2 Hexagonal Description: Quartz is the most abundant mineral. It is an essential component of granitic igneous rocks, of sedimentary rocks such as sandstone and chert and of metamorphic rocks such as quartzites. It is a …