Formula: (Ce,Ca,Th)4(Fe,Mg)(Ti,Mg,Fe)4Si4O22 Monoclinic Description:Chevkinite-(Ce) is a group of minerals related by complex solid solution substitution. It is found in Wisconsin as accessory minerals in the igneous rocks of the Wausau Complex.MARATHON COUNTY: Buchholz et. al (2011) reports 3 …
Marathon 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. …
Columbite-Tantalite
Formula: (Fe,Mn)(Nb,Ta)2O6 Orthorhombic Description: Columbite-(Fe) in tabular crystal from the Nine Mile pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Image courtesy Al Falster.) Columbite-tantalite refers to a group of minerals having varying amounts …
Cookeite
Formula: LiAl4(AlSi3010)(OH)8 Monoclinic Description: Cookeite is a rare alteration product of other lithium minerals found in complex granitic pegmatites. MARATHON COUNTY: White micaceous material found in a pocket in a pegmatites in the Wausau pluton, has been tentatively …
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 …
Cryolite
Formula: Na3AlF6 Monoclinic Description: Cryolite and prosopite from the Nine Mile pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo courtesy Al Falster.) Cryolite is a very rare mineral found in fluorine-enriched pegmatites. MARATHON COUNTY: Cryolite …
Diopside
Formula: CaMgSi2O6 Monoclinic Description: Diopside occurs in moderate to high-grade metamorphic rocks. It is particularly common in marbles, calc-silicate rocks, and amphibolites. FLORENCE COUNTY: Found with tremolite in marble from a drill core into a metasedimentary sequence from …
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 …
Erythrite
Formula: Co3(AsO4)2.8H20 Monoclinic Description: Erythrite is a pink to purple powdery to acicular mineral formed as a result of near-surface alteration of other cobalt-rich minerals. LAFAYETTE COUNTY: Erythrite was tentatively reported as intermixed with melanterite as an …
Euclase
Formula: BeAlSiO4(OH) Monoclinic Description: Euclase is a rare mineral found in complex granite pegmatites. MARATHON COUNTY: Euclase is reported in the granite pegmatites cutting the Wausau complex (Falster, correspondence 1986, WGNHS files).