Formula: (Al2O3)(SiO2)1.3-2.2.5-3H2O Amorphous Description: Allophane is a clay mineral with the general chemical composition of kaolinite but lacking a crystalline structure. It is formed by the breakdown of other alumino-silicates, such as feldspar, due to weathering …
Dodge County
Andalusite
Formula: Al2SiO5 Orthorhombic Description: Andalusite is found in phyllites, schists and gneisses and associated quartz veins. It indicates relatively low pressure metamorphism of aluminum-rich rocks, such as shales. ASHLAND COUNTY: Andalusite occurs as “chiastolite” in fine-grained schists outcropping …
Apatite Group
Formula: Ca5(PO4)3(F,Cl,OH) Hexagonal Description:Apatite denotes a family of minerals referred to variously in older literature as “fluorapatite,” “chlorapatite,” “carbonate-apatite” or “hydroxlyapatite” and in newer literature as apatite- (CaF) etc. depending on which anion group dominates. Members …
Aragonite
Formula: CaCO3 Orthorhombic Description: Aragonite forms in low temperature hydrothermal deposits, especially as sinter around hot springs and amygdules in basalts. It also occurs as speleothems, as organic or inorganic precipitates in marine sediments. Finally, it forms …
Bismuth
Formula: Bi Hexagonal Description: Bismuth crystal cluster on quartz. Waterloo Quarry, Dodge County, Wisconsin. SEM image from the University of New Orleans. (Photo by Tom Buchholz.) Bismuth is a silvery metallic mineral that occurs rarely in …
Bismutomicrolite
Formula: BiTa2O6(OH) Isometric Description: Bismutomicrolite is a very rare mineral found in hydrothermally mineralized pegmatites. DODGE COUNTY: Bismutomicrolite occurs as tiny grains embedded in feldspar in a pegmatite dike cutting quartzite in the Michels Materials Waterloo Quarry, …
Calcite
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 …
Chloritoid
Formula: (Fe,Mg,Mn)Al2(SiO4)O(OH)2 Monoclinic Description: Chloritoid forms small green platy to micaceous grains in rocks that have been subjected to moderate grades of regional metamorphism. It may also form by hydrothermal alteration of rocks. It occurs with muscovite, …
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 …
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 …