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, …
Ashland County
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. …
Clinozoisite
Formula: Ca2Al3(Si2O7)(SiO4)O(OH) Monoclinic Description: Common in low-grade metamorphic rocks, particularly as an alteration product of plagioclase. ASHLAND COUNTY: Formed as an alteration product of plagioclase in the gabbros near Mellen, where it forms with epidote, zoisite, calcite …
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 …
Cubanite
Formula: CuFe2S3 Orthorhombic Description: Cubanite is a relatively rare mineral found high temperature ore deposits. It is often associated with chalcopyrite and pyrrhotite. Cubanite often occurs as oriented growths within chalcopyrite, and, as such, can often be …
Cummingtonite
Formula: (Mg,Fe)7Si8O22(OH)2 Monoclinic Description: Cummingtonite is a member of the amphibole family. It commonly forms elongated to fibrous green to brown grains in metamorphosed iron-rich rocks. ASHLAND COUNTY: Cummingtonite is found in the Ironwood Iron Formation where it …
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 …
Epidote
Formula: Ca2(Al2Fe3+)(Si2O7)(SiO4)O(OH)2 Monoclinic Description: Epidote is a common mineral formed during low grades of metamorphism and hydrothermal activity. It is particular common in metamorphosed basalts and gabbros where it replaces plagioclase, pyroxene and olivine. It can also …
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 …