Formula: Na15Ca6(Fe,Mn)3Zr3Si25O73(O,OH,H2O)3(OH,Cl)2 Hexagonal Description: Eudialyte is a rare mineral found in pegmatitic low-silica igneous rocks. MARATHON COUNTY: Pale yellow anhedral grains of eudialyte with locally pinkish cores were found in a gneissic syenite in the NE NE Sec. …
Marathon County
Euxenite-(Y)
Formula: (Y, Ca, Ce,U, Th)(Nb,Ta,Ti)2O6 Orthorhombic Description: Euxenite-(Y) from the Nine Mile pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Image courtesy Al Falster) Euxenite is an uncommon mineral found in complex granitic pegmatites. …
Ferberite-huebnerite Series
Formula: (Fe,Mn)WO4 – Monoclinic Description: The ferberite-huebnerite series is a series of tungstate minerals with varying proportions of iron to manganese. They are relatively high temperature minerals characteristically found in quartz veins associated with granite. MARATHON COUNTY: …
Fergusonite-(Y)
Formula: YNbO4. Tetragonal Description: Fergusonite-(Y) is a rare earth mineral found in granitic and other pegmatites. It may also be found in placer deposits from the weathering and erosion of such bodies. MARATHON COUNTY: Tiny acicular crystals …
Florencite-Ce
Formula: CeAl3(PO4)2(OH)6 Hexagonal Description: Florencite-Ce is a very rare member of the cradallite group. MARATHON COUNTY : Florencite-Ce was found as microscopic grains intergrown with quartz in a greisen zone in the Magurie Pit, part of the LaDick …
Fluorite
Formula: CaF2 Isometric Description: Fluorite crystals, from Sturgeon Bay in Door County, Wisconsin. Field of view is about 4 cm. (Image courtesy W. S. Cordua.) Fluorite often forms coarse cleavable masses or cubic crystals. It can take …
Galena
Formula: PbS Isometric Description: Galena crystals surrounded by marcasite, from Shullsburg, Wisconsin. (Image courtesy W. S. Cordua.) Galena is formed in a wide range of hydrothermal environments. It can be found with sphalerite and chalcopyrite in …
Goethite
Formula: FeO(OH) Orthorhombic Description: Stalactitic goethite from Montreal Mine in Iron County, Wisconsin. (Image courtesy W. S. Cordua.) Goethite is a common iron mineral. It often forms by weathering of other iron-rich minerals, thus is a …
Gold
Formula: Au Isometric Description:Gold is usually found in hydrothermal deposits where it forms at a wide range of temperatures and geological settings. Gold may form in exhalative deposits formed on the sea floor associated with Archean …
Gorceixite
Formula: BaAl3(PO4)2(OH)5.H2O Monoclinic Description: Gorceixite is a very rare member of the cradallite group. MARATHON COUNTY: Gorceixite was found as tiny grains intergrown with sulfides in a greisen zone in the Magurie Pit, part of the …