Formula: Bi2S3 Orthorhombic Description: Bismuthinite is a rare mineral associated with hydrothermal veins in granitic environments. WOOD COUNTY: Bismuthinite occurs as rare tiny fibers in calcite in veins cutting granite exposed in the Haske quarry in Sec. …
Wood County
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 …
Brucite
Formula: Mg(OH)2 Hexagonal Description: Brucite forms as a result of the alteration or low-grade metamorphism of other magnesium-rich minerals, such as olivine and periclase. It is usually found in ultramafic rocks and marbles with serpentine, dolomite, hydromagnesite …
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 …
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 …
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, …
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 …
Chlorite Group
Formula: (Al, Fe, Li, Mg, MN, Ni, Zn)6 (Si, Al)4O10(OH, O)2 MONOCLINIC or TRICLINIC Description: Chlorite represents a group of over 10 minerals related by complex solid solution substitutions. These minerals are generally fine-grained, micaceous and dark green. …
Chromite
Formula: FeCr2O4 Isometric Description: Chromite occurs as small grains in ultramafic rock associated with serpentine, talc, magnesite and brucite. It is an important ore of chromium when found in quantity. CLARK COUNTY: A minute black metallic grain in …