Formula: FeS2 ISOMETRIC
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 of pyrite in the state will be recorded here.
ASHLAND COUNTY: Pyrite is a common accessory mineral in the Bad River dolomite, such as is found at Penokee Gap in the SE NW Sec. 14 T.44N. R.3W. (Van Hise and Irving, 1892).
BROWN COUNTY: Pyrite is abundant in the dolostones and shales associated with the oolitic iron ore of the Neda Formation. This outcrops, for example, on the north side of County G SE NE Sec. 32 T23N R21E near Bellevue (WGNHS outcrop descriptions).
— Chamberlain (1877) notes oolitic pyrite found along the river gorge northeast of Cascade Falls E of DePere.
CALUMET COUNTY: Pyrite occurs in the dolostones of the Silurian Burnt Bluff Group. These are exposed, among other places, in a quarry at the center of Sec. 18 T13N R17E near Nasbro and in a quarry in the NW Sec. 25 T18N R19E, 1 mile S of Chilton (Soderman and Carozzi, 1963).
CRAWFORD COUNTY: Cubo-octahedral crystals of pyrite up to 3 cm across, now completely replaced by goethite, occur on chert in the Oneota dolostones in a quarry near Steuben. They are also associated with large rosettes of marcasite, also replaced by goethite (Phil Burgess, 1989, personal communication).
DODGE COUNTY: Pyrite occurs in the dolostones of the Silurian Burnt Bluff Group. These are exposed, among other places, in a quarry 1.5 miles N of Knowles (Soderman and Carozzi, 1963).
— Vertical veins of pyrite and marcasite up to 30 cm. thick cut Galena and Decorah formation sediments in a quarry in sec. 8 T.10N. R.14E. (Brown and Maas, 1992).
DOOR COUNTY: Pyrite occurs in the dolostones of the Silurian Burnt Bluff Group. These are exposed, among other places, in a quarry 2 miles N of Sturgeon Bay (Soderman and Carozzi, 1963).
—Pyrite as crystals and replacing fossils in limestone occurs in float on the beach and in outcrop at low water along Lake Michigan 2 miles N of Whitefish (Nelson and Roberts, 1963).
FOND DU LAC COUNTY: Pyrite and calcite xls occur in cavities in the limestone of the Galena Formation exposed at Moore’s Quarry in the west part of Fond du Lac (Chamberlain, 1877).
— Globular to well-formed aggregates of crystals were found washing out of Cincinnatian shales at the base of Taycheedale Falls in the NW Sec. 21 T15N R17W in Fond du Lac (Chamberlain, 1877).
— Pyrite occurs in limestone as tiny, sometime iridescent, crystals in vugs and on joint surfaces at the Ripon Lime and Materials Company Quarry, NW sec. 20 T.16N R.14E., just west of Ripon.
FOREST COUNTY: Pyrite is a major component of the massive sulfide ore and underlying stringer ore at the Crandon massive sulfide deposit near Little Sand Lake. Individual grains, cubic to spherical in habit, are rarely more than a few mm in diameter (May and Schmidt, 1982; Lambe and Rowe, 1989).
GRANT COUNTY: Pyrite is widespread at the many mines and prospects of the Upper Mississippi Valley zinc-lead district, where it is associated with marcasite, galena, sphalerite, calcite, dolomite and other minerals. The following description is drawn from Heyl, et al., (1959). Pyrite is often the first mineral formed in these deposits. This early generation forms small octahedral crystals and masses replacing wall rocks at times 20 feet away from the main vein. Pyrite also forms rinds up to several inches thick on the outer walls of the veins. Later pyrite generations often form “radiating crystals composed of greatly attenuated cubes”. A colloform habit and a late cubic generation are also ubiquitous throughout the deposits. The pyrite often alters to iron oxides. This is true of the deposits in Iowa and Lafayette Counties, as well as Grant County. Only a few of the more notable pyrite occurrences in Grant County are described. Most of the localities given for marcasite, sphalerite and galena in Grant County are also pyrite localities.
— Masses and well-formed crystals of pyrite are found throughout the Platteville district. Several important localities are the Depp or Fever River Mine in the Platteville District in the S 1/2 NE Sec. 18 T2N R1E and the Rasque ore body in the NW Sec. 36 T3N R1W (Heyl, et al., 1959).
— Pyrite was mined with marcasite, as iron ore at the Johns Mine S 1/2 SE Sec. 26 T.6N. R.1W. near Montford (Heyl, et al., 1959).
— Pyrite is found at the Piquette #2 SW NE Sec. 36 T3N R3W near Tennyson (Heyl, 1964).
IOWA COUNTY: Pyrite is common throughout the county at the many mines and prospect pits of the Upper Mississippi Valley zinc-lead district. The general comments on pyrite habits listed under Grant County also apply to Iowa County. Only a few of the many localities can be listed here. Most of the listings under marcasite, galena and sphalerite for this county are also pyrite localities.
— Cubes of pyrite.0.75 cm on an edge, often elongated into subparallel needle-like aggregates occur with sphalerite in the Mineral Point area (Hobbs, 1895). Raasch (1924) describes similar bladed crystals from the region which may be 4 cm long. Raasch also notes “sheaf-like arborescent clusters” of pyrite encrusted with smithsonite from the Mineral Point area.
— Unmodified pyrite cubes up to 1/2 cm across occur at Etna (Hobbs, 1895).
— Large pyrite crystals, now replaced pseudomorphically by goethite, are found at the Oehlerking Mine, NW SE Sec 31 T.7N. R.1E. near Highland (Heyl, et al., 1959).
— Pyrite is abundant in the mines of the Rewey and Mifflin quadrangles. Some specific localities are the Ebenezer Mine (SW SW Sec. 30 T5N R1E) and the New Dale Rundell Mine (SE NE Sec. 31 T5N R1E) (Taylor, 1964). Pyrite also occurs at the Defense Mine (E 1/2 SW SW Sec. 28 T5N R1E) near Mifflin. Here large botryoidal masses occur with sphalerite (Heyl, et al., 1959).
— A nickel-bearing pyrite (bravoite) was found as tiny grains intergrown with violarite in coating or replacements of primary millerite in the Linden District. This is particularly true in the zinc mines in sec. 8 and 18 T.5N. R.2E. (Heyl et al., 1959). Associated minerals were marcasite, galena and sphalerite. The “bravoite” and violarite were in turn partly altered to other nickel minerals such as honessite.
JEFFERSON COUNTY: Pyrite is a found as small cubo-octahedral crystals with marcasite, dolomite and calcite in vugs in the Galena formation in the Hausz Brother’s Quarry, near Fort Atkinson. (WSC field notes).
JACKSON COUNTY: Pyrite is a component of the talc schist and mica schists at the Jackson County Iron Mine east of Black River Falls, SE Sec. 15 T21N R3W. The pyrite occasionally forms euhedral cubes several cm. across. (WSC field notes).
KENOSHA COUNTY: Pyrite occurs in a subsurface, diamond-bearing lamprophyre diatreme, discovered within the outskirts of Kenosha. (Carlson and Adams, 1997.).
LAFAYETTE COUNTY: Pyrite is common in the many mines and prospects of the Upper Mississippi Valley zinc-lead district. The general comments under Grant County also apply to Lafayette County. Only a few of the more important localities will be listed here. Any of the marcasite, galena or sphalerite localities listed are also potential pyrite localities.
— Pyrite is abundant in the Shullsburg district, where it replaces dolomitic country rock, forms rinds on ore veins, and makes euhedral crystals, including radiating masses (McLimans, Barnes and Ohmoto, 1980). Hobbs (1895) describes crystals from the Wisconsin zinc and lead mine near Shullsburg as dominated by the positive pyritohedron with cube and octahedron modifications.
— Pyrite is found at the Gabriel Mills diggings (Sec. 29 T1N R1E) and the Simmon and Sons Mine (NE NW Sec. 32 T1N R1E (Strong, 1877).
— Pyrite is found at the Thompson-Temperley Mine, New Diggings (Sec. 27 T1N R1E) (Hosterman, Heyl and Holly, 1964).
— Pyrite is abundant at the Teasdale Mine near Cuba City (Sec. 21 T1N R1E) and at the Blackstone Mine near New Diggings (Sec. 28 T1N R2E) (Zimmermann, 1969).
— Pyrite is abundant at the Dall Mine (Sec. 22 T2N R1E) where it occurs as radiating rectangular crystals and masses with sphalerite (Klemic and West, 1964).
— A nickel-rich pyrite (“bravoite”) is reported as a component of the zinc-lead ores in the Belmont and Calamine Districts. (Klemic and West, 1964). “Bravoite” was also found at the Farrey Mine near Benton (NW sec. 14 T.1N. R.1E) where it is associated with violarite, calcite and chalcopyrite. (Heyl et al., 1959).
MANITOWOC COUNTY: Pyrite occurs as cubes, octahedra and pyritohedra, sometimes iridescent, with calcite, fluorite, marcasite and strontianite in vugs in dolostone in the quarry on the north edge of Valders. (Carl Cochrane, 1999, perssonal communication)
MARATHON COUNTY: Massive pyrite in bedrock is found in a gravel pit east of Hwy 34 in the SW Sec. 32 T26N R7E near Darcy (LaBerge and Myers, 1983).
— Pyrite is found at the old gold mine site east of the Eau Claire River near Eason, just SW of the center of Sec. 26 T29N R9E. Here it is associated with chalcopyrite and quartz in veins in chlorite schist (LaBerge and Myers, 1983).
— Pyrite was originally a component of many of the pegmatites of the Nine Mile Granite, but has now been replaced by iron oxides. It still exists as pyrite as tiny inclusions in smoky quartz in these pegmatites. The crystals may be cubes or elongated crystals (Falster et al., 2000).
MILWAUKEE COUNTY: Pyrite nodules are found weathering out of bedrock in Milwaukee in the “hill behind the Dillon Motel and Hall Chevrolet” (Zeitner, 1988).
— Pyrite nodules occur in outcrop at the SW corner of state highway 100 and North Avenue in Wauwatosa (Brown, personal communication, 1996).
— Brilliant crystals of pyrite, forming cubes and octahedra occurs in vugs in the Milwaukee Formation at Estabrook Park, Milwaukee (Sec. 5 T.7N. R.22E.). The pyrite occurs with millerite, marcasite, calcite and sphalerite (Bagrowski, 1940).
ONEIDA COUNTY: Pyrite is a major component of the massive sulfide ore and adjacent wall rock and stringer zones of the Pelican Deposit, east of Rhinelander in Sec. 29 T.36N. R.9E. It is here intergrown with sphalerite and chalcopyrite (Mudrey, 1979).
— Pyrite is found disseminated in a chloritized lithic crystal tuff in a road cut on old US Hwy 8 (SE NW Sec. 26 T.36N. R.10E.) west of Monico (Mudrey, 1979).
— Pyrite is a component of the metamorphosed mafic pillow lava in a roadcut east of Monico at the intersection of county V and old US Hwy 8 (center Sec. 29 T36N R11E) (Mudrey, 1979). ,p> OUTAGAMIE COUNTY: Pyrite occurs in cavities and fissures with calcite in a quarry near Kaukauna (Chamberlain, 1877). – Pyrite is found in the Murphy Seymour Quarry (NE SE sec. 31 T.24N. R.18E). This pyrite is arsenical and its oxidation contributes significant arsenic to the local ground water. (Dutch, et. al., 1997).
PEPIN COUNTY: Small pyrite pyritohedrons with cube and octahedron modifications, now replaced by goethite, occur at a quarry on County J (NW NW Sec. 7 T23N R15W) north of Stockholm (W. S. Cordua field notes).
PIERCE COUNTY: Pyrite crystals, with individuals over 2 cm across and clusters, now almost entirely replaced by goethite occur in Prairie du Chien dolostones in a quarry on Cady Creek (SE SW SE Sec. 3 T.27N. R.15W.) SE of Spring Valley. Octahedrons and cubes modified by octahedrons both occur with drusy tan dolomite and white quartz crystals (W. S. Cordua field notes).
RACINE COUNTY: Pyrite occurs in geodes with calcite and also disseminated through adjacent limestone at the rapids of the Root River, Racine (Chamberlain, 1877).
Cubo-octohedral pyrite crystals up to 2.5 cm across occur in vugs in limestone at the Ives Quarry in Racine. Pyrite also outlines phantoms in large calcite crystals here (Scovil, 1994). Pyrite also occurs as replacements of brachiopod sheels
Well crystallized pyrite was found in geodes at Vaughn’s Quarry in Racine (Chamberlain, 1877).
— Pyrite as radiating clusters (“sun dollars”) occur at the Warren Peter’s Quarry near Burlington.
RICHLAND COUNTY: Cubic pyrite crystals modified by octahedron and now replaced by goethite are found on hillcrests north of the Wisconsin River (North, 1913).
RUSK COUNTY: Pyrite is a major mineral in the massive sulfide, disseminated and stringer ore bodies in the Flambeau deposit, near Ladysmith (May, 1977). Most of the pyirite is massive, but small cubes do occur in vuggy regions. The pyrite is often partially replaced by chalcocite and other copper sulfides in the mined supergene zone.
TAYLOR COUNTY: Pyrite is abundant at the Bend massive sulfide deposit NW, sec. 2 T.32N. R.2W. northeast of Gilman. It is associated with bornite, chalcopyrite and gold tellurides. (DeMatties and Rowell, 1991).
WAUKESHA COUNTY: Pyrite occurs abundantly in black shale and interbedded limestone at the Roberts Quarry on the south side of Peawaukee Lake. At one time, this was prospected unsuccessfully for coal (Chamberlain, 1877).
WAUPACA COUNTY: Large masses of goethite after pyrite occurs in a pegmatite exposed in a highway expansion on County G near Weller Lake, east of Big Falls (Tom Buchholz, 2002).
WINNEBAGO COUNTY: Pyrite is found in cavities and veins in the Lutz Quarry, in the western part of Oshkosh. The pyrite occurs in “an unusual variety of forms and colors” (Chamberlain, 1877) associated with sphalerite, galena, marcasite and calcite (USGS, 1976).
— Pyrite crystals with marcasite, calcite and, rarely, sphalerite occur in vugs in the Platteville Formation in the Grundy Quarry, NE NW NE Sec. 33 T.19N. R.16E. (UW Oshkosh, 1989).
— Iridescent pyrite cubes and pyritohedrons occur with calcite, fluorite and dolomite in vugs and veins in dolostones in the quarries along the SE edge of Neenah, just west of Lake Winnebago (Bagg, 1918).
— Iridescent pyrite crystals occur with marcasite, calcite, dolomite and fluorite in vugs in dolostone in the quarries on Tullar road, in Neenah. (Carl Cochrane, 1999, personal comunication).
WOOD COUNTY: Pyrite is common as micro crystals showing cube, octahedron and pyritohedron forms in vuggy veins cutting granite at the Frederich Schill Quarry, NE of Vesper on the E side of Hwy 180. Some unusual microcrystals show acicular habits of stacked cubes (Buchholz,1999).
— Occurs as masses, euhdral cubes up to 3 cm. in diameter and occasional acicular xls. in vugs in the granite of the Haske Quarry, (SW SE sec. 25 T.24N. R.2E.). It is also found as small xls. in vugs (Buchholz et al., 1998, 2007d).