Formula: Fe2+Fe3+2O4 Isometric Description: Magnetite is a common mineral found at many localities in Wisconsin. Only localities that where the mineral is present in great abundance or as unusual material are listed here. Magnetite occurs as an …
Ashland County
Minnesotaite
Formula: (Fe,Mg)3Si4O10(OH)2 Triclinic Description: Minnesotaite is found frequently as small grains in iron formations that have experienced low grade metamorphism. It is often associated with stilpnomelane, cummingtonite, chlorite and siderite. Wisconsin localities for this minerals are restricted …
Molybdenite
Formula: MoS2 Hexagonal Description: Molybdenite is a relatively common hydrothermal mineral. It is most often found in vein complexes associated with granitic igneous rocks and related skarns that form at medium to high temperatures. It is economically …
Nickeline
Formula: NiAs Hexagonal Description: Nickeline, also referred to as “niccolite”, is a rare mineral found in high temperature hydrothermal deposits, especially those in mafic igneous rocks. Other nickel minerals, pyrrhotite and chalcopyrite are commonly associated. ASHLAND …
Olivine
Formula: (Mg,Fe)2SiO4 Orthorhombic Description: Olivine is here used to refer to a solid solution series of minerals ranging from the magnesium end member (forsterite) to the iron end member (fayalite). Olivine is widespread in basalts and gabbros, …
Orthopyroxene
Formula: (Mg,Fe)SiO3 Orthorhombic Description: Orthopyroxenes are a group of minerals ranging from pure MgSiO3 (enstatite) to pure FeSiO3 (ferrosilite). Bronzite and hypersthene are orthopyroxenes mid-way between these two end members. As the particular orthopyroxene mineral described is not always …
Pentlandite
Formula: (Fe,Ni)9S8 Isometric Description: Pentlandite is a bronzy metallic mineral found intergrown with other sulfides such as pyrrhotite and pyrite. ASHLAND COUNTY: Pentlandite is found intergrown with chalcopyrite, pyrrhotite, cubanite and other minerals in copper-nickel massive sulfide body …
Pigeonite
Formula: (Mg,Fe,Ca)(Mg,Fe)Si2O6 Monoclinic Description: Pigeonite is a member of the pyroxene group found generally as small grains in gabbros, basalts, andesites, dacites and hornfels. It occurs with plagioclase and augite, and is difficult to identify. It is …
Plagioclase
Formula: CaAl2Si2O8 Triclinic Description: Plagioclase is a family of feldspar minerals forming a solid solution that ranges, relatively continuously, from pure sodium aluminum silicate (the end member called albite) to pure calcium aluminum silicate (the end member …
Potassium Feldspar
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 …