Formula: Mixture of pyrophillite and sericite. Description: Pipestone is a compact pink to red metamorphosed mudstone (or argillite) of a consistency that allows it to be carved into pipes and other art objects. It is found as …
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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 …
Phosphosiderite
Formula: FePO4.2H2O Monoclinic Description: Lavender-colored coatings of phosphosiderite in matrix of other black-altered phosphate minerals. From the Stewart Mine, near Pala, San Diego County, California. (Photo by W. Cordua.) Phosphosiderite forms reddish or purplish elongated to radial …
Phlogopite
Formula: KMg3(AlSi3O10)(OH)2 Monoclinic Description: Phlogopite is a tan mica found most often in magnesium-rich rocks such as marbles, calc-silicate and ultramafic rocks. KENOSHA COUNTY: Phlogopite occurs in a subsurface, diamond-bearing lamprophyre diatreme, discovered within the outskirts of Kenosha …
Phillipsite
Formula: (K,Na,Ca,Ba)4-7(Al4-7Si12-9)O32.12H2O Monoclinic Description: White phillipsite-K crystals on matrix. From Nickel Quarry, Oberwiddersheim, Hungen, Volgelsburg, Hesse, Germany. Specimen is 4.5 x 4.5 x 2 cm in size. (Photo courtesy Dan and Diana Weinrich Minerals; unauthorized reproduction is …
Petzite
Formula: Ag3AuTe2 Isometric Description: Petzite is a steel-gray granular mineral found in hydrothermal deposits associated with other rare tellurium, gold and silver minerals. RUSK COUNTY: Petzite is reported as a component of the ore at the Flambeau Mine, …
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 …
Pectolite
Formula: NaCa2(HSi3O9) Triclinic Description: Pectolite usually forms from hydrothermal fluids as a vein or amygdule filling in basaltic volcanic rocks. It may also form in silica poor syenites and marbles. BAYFIELD COUNTY: Pectolite occurs as white fibers …
Pearls
Description: Pearls are hard nodular precipitates formed inside the shells of mollusks such as clams. They consist of layers of calcium carbonate, either in the form of calcite or aragonite held together by a horny …
Osarizawaite
Formula: Pb(AlCu)3(SO4)2(OH)6 Hexagonal Description: Osarizawaite is a rare secondary mineral found in the zone of oxidized over lead-bearing deposits. RUSK COUNTY: Osarizawaite occurs in the oxidized zone at the Flambeau Mine, near Ladysmith (Jones, Jones, and LaBerge, 1999).