Formula: Mg3Al2(SiO4)3 Isometric Description: Pyrope is a magnesium-rich member of the garnet group found in rocks such as lamproites, anorthosite, serpentinite and their metamorphosed equivalents. It may survive weathering as a heavy detrital mineral. The chromium-rich member …
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Pyromorphite
Formula: Pb5(PO4)3Cl Hexagonal Description: Pyromorphite. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 861. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by Andrew Silver.) Pyromorphite is …
Pyrolusite
Formula: MnO2 Tetragonal Description: Pyrolusite forms as a weathering product of other manganese minerals, as concretions or dendrites deposited by ground water or as nodules precipitated from lake water. Pyrolusite is often soft and soils the fingers, …
Pyrochlore Group
Formula: (Ce, Ca, Y)2Nb2O6(OH,F) Isometric Description: Pyrochlore is a group of rare minerals found in pegmatitic granites, syenites, and carbonatites. MARATHON COUNTY: Pyrochlore group mineral can be found as tiny grains in the Stettin Pluton and Nine-Mile …
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 …
Pyrargyrite
Formula: Ag3SbS3 Hexagonal Description: Pyrargyrite is a deep red to nearly black mineral found in hydrothermal veins often associated with other silver minerals, galena, pyrite and quartz. ONEIDA COUNTY: Pyrargyrite occurs at the Lynn massive sulfide deposit, in …
Pumpellyite Group
Formula: Ca2(Fe2+,Mg)Al2(SiO4)(Si2O7)(OH)2.H2O Monoclinic Description: Pumpellyite is used to denote a group of closely related minerals that form during relatively low grade burial metamorphism. It is often associated with prehnite, epidote and chlorite. It is most common …
Psilomelane
Formula: Mixture of hydrate manganese-barium oxides Description: Psilomelane is used as a blanket term to denote a variety of hard massive mixtures of manganese oxides. Most, but not all, psilomelane is the mineral romanechite (BaMn2+Mn4+8O16(OH)4 ). The …
Pseudorutile
Formula: Fe2Ti3O9 Description: Pseudorutile generally forms as an alteration product of ilmenite during weathering, especially in tropical environments. It has recently been documented as a mineral formed during low-grade metamorphism. SAUK COUNTY: Pseudorutile was found as tiny …
Pseudomalachite
Formula: Cu5(PO4)2(OH)4 Monoclinic Description: Pseudomalachite is a green hydrated copper phosphate formed as a secondary mineral in the oxidized zone of copper deposits. RUSK COUNTY: Pseudomalachite occurs as rare masses and spherical rosettes of drusy crystals in the …