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 …
Rusk County
Carrollite
Formula: Cu(Co,Ni)2S4 Isometric Description: Carrollite is gray metallic sulfide mineral containing copper, cobalt and nickel formed in hydrothermal deposits. RUSK COUNTY: Carrollite has been tentatively identified as silvery black crystals on dolomite from the carbonate zone of the …
Chalcanthite
Formula: CuSO4.5H2O TRICLINIC Description: Chalcanthite usually forms as crusts on other copper minerals during weathering. It is a water soluble mineral that does not survive long in Wisconsin’s climate. RUSK COUNTY: Sky blue coatings of chalcanthite were …
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, …
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. …
Chrysocolla
Formula: (Cu,Al)2H2Si2O5(OH)4.nH2O Monoclinic Description: Chrysocolla is a blue copper-rich clay mineral that forms as an alteration product of other copper minerals in supergene and oxidized zones. IOWA COUNTY: Reported at the Steppler Farm, 4 miles SW of …
Copper
Formula: Cu Isometric Description: Native copper occurs as veins and cavity fillings in hydrothermally altered basaltic igneous rocks. It is also a product of near-surface supergene alteration of other copper minerals, such as chalcopyrite. Copper can …
Cordierite
Formula: (Mg,Fe)2Al3(AlSi5O18) Orthorhombic Description: Cordierite is found in many medium-grade metamorphic environments. It is often found in the high temperature-low pressure zones in contact metamorphic halos. In Wisconsin, however, it most often is found in schist …
Corundum
Formula: Al2O3 Hexagonal Description: Corundum is most famous for its rare colored varieties: the bright red ruby and the deep blue sapphire. More often, it is found as drabber blue to blue-gray crystals. Corundum forms in rocks …