Formula: (Co,Fe,Ni)As2 Orthorhombic Description: Safflorite is a rare gray metallic mineral forming prismatic to radially fibrous crystals in hydrothermal veins. It is characteristically associated with minerals bearing cobalt, nickel or arsenic such as cobaltite and arsenopyrite. LAFAYETTE …
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Rutile
Formula: TiO2 Tetragonal Description: Rutile from the Nine Mile Pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo by Al Falster.) Rutile is an accessory mineral found in a wide variety of rocks, usually as …
Riebeckite
Formula: Na2(Fe32+3Fe3+2)Si8O22(OH)2 Monoclinic Description: Riebeckite is a sodium-rich member of the amphibole family. It typically forms dark blue elongated to fibrous crystals in highly sodic granites, syenites, iron formations and schists. JACKSON COUNTY: Minor riebeckite occurs in the …
Rhodochrosite
Formula: MnCO3 Hexagonal Description: Rhodochrosite is an attractive pink mineral formed generally by hydrothermal processes associated with igneous activity or the metamorphism of manganese-rich rocks. IRON COUNTY: Rhodochrosite was found at the Montreal Mine as crystals, druses and …
Rhodizite
Formula: (K,Cs)Al4Be4(B,Be)12O28 Isometric Description: Rhodizite is an extremely rare mineral forming colorless, white to yellowish crystals in complex pegmatites. FLORENCE COUNTY: Rhodizite is reported as small euhedral crystals in the “Animikie Red Ace Pegmatite”, most likely the lithium-rich …
Rhabdophane Group
Formula: (Nd,Ce,La)PO4•H2O Hexagonal Description: Rhabdophane in elongated crystals from the Nine Mile Pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo by Al Falster.) Rhabdophane-(Ce) from the Nine Mile Pluton near Wausau in Marathon …
Reidite
Formula: ZrSiO4 Tetragonal Description: Reidite, a polymorph of zircon, is an extremely rare mineral that forms under very high pressures, such as are associated with large extraterrestrial impact structures (meteor craters). PIERCE COUNTY: Reidite has been documented by …
Quartz
Formula: SiO2 Hexagonal Description: Quartz is the most abundant mineral. It is an essential component of granitic igneous rocks, of sedimentary rocks such as sandstone and chert and of metamorphic rocks such as quartzites. It is a …
Pyrrhotite
Formula: Fe1-xS Monoclinic Description: Pyrrhotite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 867. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by …
Pyrophyllite
Formula: Al2Si4O10(OH)2 Monoclinic Description: Pyrophyllite is a micaceous mineral formed as a result of the relatively low grade metamorphism of aluminum-rich rocks. It can also form as a hydrothermal replacement of aluminous minerals such as feldspars. The …