Formula: KAlSi3O8 Monoclinic or Triclinic Description: Potassium feldspar refers to any of the three polymorphs microcline, orthoclase or sanidine. The distinction between these minerals can be made with certainty only after detailed X-Ray analysis. This has not …
Dodge 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 …
Pyrophyllite
Formula: Al2Si4O10(OH)2 Monoclinic Description: Pyrophyllite is a micaceous mineral formed as a result of the relatively low grade metamorphism of aluminum-rich rocks. It can also form as a hydrothermal replacement of aluminous minerals such as feldspars. The …
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 …
Siderite
Formula: FeCO3 Hexagonal Description: Siderite forms as a sedimentary precipitate, in hydrothermal veins, in metamorphic rocks formed from such protoliths, and, rarely, in pegmatites. In sedimentary environments it forms in extensive beds of banded iron formations …
Spessartine
Formula: Mn3Al2(SiO4)3 Isometric Description:Spessartine is a member of the garnet family. It is usually red to orange in color and is found generally in granite pegmatites, where it can form large gemmy crystals. It is also found …
Sphalerite
Formula: ZnS Isometric Description: Banded sphalerite, near Hazel Green in Lafayette County, Wisconsin. Sample is about 1 cm long. Sphalerite occurs in a wide range of hydrothermal environments. It is common with chalcopyrite in exhalative massive …
Stevensite
Formula: (Ca,Na)xMg3-x(Si4O10)(OH)2 Monoclinic Description: Stevensite is a massive white clay mineral. IMA lists its species status as questionable. DODGE COUNTY: A white waxy mineral forming elongated grains in the matrix of the Mayville iron ore was tentatively identified …
Tourmaline Group
Formula: Na(Al,Fe,Li,Mg,Mn)3(Al,Cr,V,Fe)6(BO3)3Si6O18(O,OH,F)4 Hexagonal Description: Tourmaline var elbaite Animikie Red Ace pegmatite (red) showing comb texture in pegmatite wall zone. With altered Cs-beryl (yellow-green). Near Fern, Florence County, Wisconsin. (Photo by Al Falster.) Tourmaline is a complex group of …
Variscite
Formula: AlPO4.2H2O Orthorhombic Description: Variscite from Clay Canyon, Fairfield, Utah. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 1162. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by …