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 …
Manitowoc County
Calcite Speleothems
Formula: CaCO3 HEXAGONAL Description: Speleothems are precipitates, usually made of calcite, in caverns. They should be conserved and not be collected from caves in order to preserve the caves’ beauty, interest and scientific values. CRAWFORD COUNTY: Abundant speleothems …
Diamond
Formula: C Isometric Description: Most diamonds form within the earth’s mantle at depths of 100 to 200 km. They are brought to the surface by the action of deep-seated magma which crystallizes to form pipe to …
Dolomite
Formula: CaMg(CO3)2 Hexagonal Description: Dolomite forms the main mineral in the bluff-forming rocks along the Mississippi River, such as Granddad Bluff near La Crosse. (Image courtesy W. S. Cordua.) Dolomite is an abundant mineral in Wisconsin. It …
Fluorite
Formula: CaF2 Isometric Description: Fluorite crystals, from Sturgeon Bay in Door County, Wisconsin. Field of view is about 4 cm. (Image courtesy W. S. Cordua.) Fluorite often forms coarse cleavable masses or cubic crystals. It can take …
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 …
Marcasite
Formula: FeS2 Orthorhombic Description: Marcasite helectite, New Diggings area, Lafayette County, Wisconsin. Sample is about 8 cm long. (Photo by W. Cordua.) Marcasite is common in Wisconsin, often found in well-formed crystals in cavities and veins in the …
Pearls
Description: Pearls are hard nodular precipitates formed inside the shells of mollusks such as clams. They consist of layers of calcium carbonate, either in the form of calcite or aragonite held together by a horny …
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 …
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 …