Formula: Pb4FeSb6S14 Monoclinic Description: Jamesonite is a metallic fibrous gray mineral formed generally from hydrothermal fluids. MARATHON COUNTY: Acicular jamesonite crystals up to 3 cm long are found in the Wausau Pluton. The jamesonite is enclosed in quartz …
Marathon County
Jarosite
Formula: KFe3(SO4)2(OH)6 Hexagonal Description: Yellow clear jarosite grains on matrix. Individual grains are about 0.05 mm across. (Dan Behnke specimen and image.) Jarosite occurs as earthy pale yellow to brown coatings, crusts and granular masses formed by the …
Kaolinite
Formula: Al2Si2O5(OH)4 Triclinic Description: Kaolinite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 689. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by Andrew …
Låvenite
Formula: (Na,Ca)2(Mn,Fe)(Zr,Ti)(Si2O7)(O,OH,F)2 Monoclinic Description: Låvenite as brown radiating crystals with black magnesio-arfvedsonite crystals in matrix. From the Kuropachii pass, Kola Peninsula, Northern Region, Russia. Specimen is 5.5 x 5.5 x 3 cm in size. (Image courtesy Dan and …
Lepidocrocite
Formula: FeO(OH) Orthorhombic Description: Lepidocrocite is a polymorph of goethite and is often found associated with it. The two minerals are very similar in physical properties, and it is likely that the mineral is more common …
Liandratite
Formula: U(Nb,Ta,)2O8 Hexagonal Description: Liandratite is a rare yellow to brown mineral found as metamict crusts in granite pegmatites. MARATHON COUNTY: Liandratite has been tentatively identified from the pegmatites at the Koss Pit (SW sec. 2 T.27 N. …
Magnetite
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 …
Malachite
Formula: Cu2(CO3)(OH2) Monoclinic Description: Malachite is a common alteration product of other copper-bearing minerals. Its bright green color makes it not only easily recognized, but also highly sought after by mineral collectors. It occurs most notable …
Microlite
Formula: (Na,Ca)2Ta2O6(O,OH,F) Isometric Description: Microlite refers to a group of rare minerals related to pyrochlore that form equant to irregular pale yellow, brown, red or green grains in complex granite pegmatites. FLORENCE COUNTY: Microlite occurs with lepidolite …
Miserite
Formula: K(Ca,Ce)4Si5O13(OH)3 Triclinic Description: Miserite is a rare mineral that forms pinkish to lavender massive compact to scaly aggregates in complex granite pegmatites. MARATHON COUNTY: Brownish-pink to white prismatic crystals of miserite up to 1 cm across are …