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 …
Door County
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 …
Fluorite
Formula: CaF2 Isometric Description: Fluorite crystals, from Sturgeon Bay in Door County, Wisconsin. Field of view is about 4 cm. (Photo by W. Cordua) Fluorite often forms coarse cleavable masses or cubic crystals. It can take on a …
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. (Photo by W. Cordua) Dolomite is an abundant mineral in Wisconsin. It is a …
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 …
Hydrocarbons
Formula: Mixtures Description: Solid hydrocarbons, generally unanalyzed in detail, are found at a number of localities within the Paleozoic rocks around the state. They may be alternately described as “bitumen” or “asphaltum”. These usually occur as …
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 …
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 …