Formula: Al3(PO4)2(OH,F)3.5H2O Orthorhombic Description: Wavellite forms as a groundwater precipitate in aluminous or ferruginous sedimentary rocks, a product of low-grade metamorphism of such rocks or in hydrothermal veins. JACKSON COUNTY: Wavellite occurs in the Eau Claire Sandstone …
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Vivianite
Formula: Fe3(PO4)2.8H2O Monoclinic Description: Vivianite is an iron phosphate mineral found in bladed crystals and clusters of an intense blue to green color. It can form in a variety of environments such as a sedimentary precipitate …
Violarite
Formula: FeNi2S4 Isometric Description:Violarite is a massive grey sulfide formed in hydrothermal deposits with other nickel minerals such as millerite. IOWA COUNTY: Violarite has been identified at several of the old zinc-lead district mines, particularly in the Linden …
Vesuvianite
Formula: (Ca,Na,vacancy)19(Al,Mg,Fe)13(vacancy,B,Al,Fe)5(Si2O7)4(SiO4)10(OH,F,O)10 Tetragonal Description: Vesuvianite most commonly forms in metamorphosed calc-silicate rocks. OCONTO COUNTY: Vesuvianite reportedly occurs with garnet, scapolite, clinopyroxene, hornblende and plagioclase in the Waupee Formation in the Mountain area. Here it is found as a …
Variscite
Formula: AlPO4.2H2O Orthorhombic Description: Variscite from Clay Canyon, Fairfield, Utah. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 1162. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by …
Uranophane
Formula: Ca(UO2)2(HSiO4).5H2O Monoclinic Description: Uranophane and petrified wood from Henry Mountains, Utah. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 1147. Courtesy of the U.S. Geological Survey Denver Library Photographic …
Uraninite
Formula: UO2 Isometric Description: Uraninite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 1134. Courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by Andrew …
Troilite
Formula: FeS Hexagonal Description: A rare sulfide generally found only in iron-nickel meteorites. ST. CROIX COUNTY: Troilite formed nodules 3- 12 mm in diameter and filled veins in the iron-nickel meteorite found in the N 1/2 SW …
Tremolite
Formula: Ca2Mg5Si8O22(OH)2 Monoclinic Description: Tremolite marble from Florence County, Wisconsin. Field of view 7 cm across. (Photo by Al Falster.) Tremolite is formed by the metamorphism of calcium-rich rocks such as limestone and dolostone. It occurs in numerous …
Tourmaline Group
Formula: Na(Al,Fe,Li,Mg,Mn)3(Al,Cr,V,Fe)6(BO3)3Si6O18(O,OH,F)4 Hexagonal Description: Tourmaline var elbaite Animikie Red Ace pegmatite (red) showing comb texture in pegmatite wall zone. With altered Cs-beryl (yellow-green). Near Fern, Florence County, Wisconsin. (Photo by Al Falster.) Tourmaline is a complex group of …