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 …
Marathon County
Boulangerite
Formula: Pb5Sb4S11 Monoclinic Description: Boulangerite is a rare hydrothermal mineral. MARATHON COUNTY: Boulangerite occurs as acicular crystals up to 2 cm long within a dike in the Wausau Pluton. These crystals show bent and twisted habits (Falster, 1987).
Brookite
Formula: TiO2 Orthorhombic Description: Brookite from the Nine Mile pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo by Al Falster.) Brookite is a relatively uncommon mineral found as an accessory in a number of …
Calaverite
Formula: AuTe2 Monoclinic Description: Calaverite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 185. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by Andrew …
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 …
Cancrinite
Formula: (Na,Ca, Vacancy)8Al6Si6O24(CO3,SO4) Description: Cancrinite forms as both a primary mineral and a secondary alteration product of nepheline in alkaline-rich igneous rocks such as syenites. MARATHON COUNTY: Cancrinite is found in the rocks of the Stettin Pluton …
Cassiterite
Formula: SnO2 Tetragonal Description: Cassiterite is a dark brown to black minerals found in granite pegmatites and high temperature hydrothermal deposits. It may also occur as a heavy mineral in alluvium. FOREST COUNTY: Cassiterite is reported as tiny …
Cerianite-(Ce)
Formula: CeO2 Isometric Description:Cerianite-(Ce) is a rare mineral occurring especially in zones where other rare-earth element-bearing minerals such as rhabdophane are exposed to secondary alteration or weathering.MARATHON COUNTY: Cerianite-(Ce) was found as extremely tiny grains intergrown with …
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, …
Cheralite
Formula: (Ca,Ce)(Th,Ce)(PO4)2 Monoclinic Description: Cheralite is a very rare mineral found in granite and syenite pegmatites. MARATHON COUNTY: A low thorium, high phosphorous cheralite is widespread in the larger pegmatite dikes of the Wausau Pluton. These are exposed …