Formula: FeTiO3 Hexagonal Description: Black opaque ilmenite with clear quartz, greenish chlorite and high-relief apatite. In rock thin section, viewed in plane-polarized light. Ilmenite grains are about 2 mm in longest dimension. Opelt Quarry, Clark County, Wisconsin. (Photo …
Dodge County
Kettnerite
Formula: CaBi(CO3)OF Orthorhombic Description: Kettnerite crystals on waylandite. From Waterloo Quarry, Dodge County, WI. SEM image by Tom Buchholz, using the SEM at the University of New Orleans. Kettnerite is a very rare mineral found as …
Koninckite
Formula: FePO4.3H2O Tetragonal Description: Koninckite is a yellow to green mineral found in association with other phosphate minerals. DODGE COUNTY: Koninckite is tentatively identified as microscopic pale yellow to olive green grains in the oolites of the …
Marcasite
Formula: FeS2 Orthorhombic Description: Marcasite helectite, New Diggings area, Lafayette County, Wisconsin. Sample is about 8 cm long. (Photo by W. Cordua.) Marcasite is common in Wisconsin, often found in well-formed crystals in cavities and veins in the …
Metavariscite
Formula: AlPO4.2H2O Monoclinic Description: Metavariscite is a pale-green mineral found as granular masses or small tabular crystals precipitated by ground water in association with other phosphate minerals. DODGE COUNTY: Metavariscite is a microscopic component of the oolites …
Muscovite
Formula: KAl2(AlSi3)O10(OH,F)2 Monoclinic Description:Muscovite is a common mica, forming silvery to pale-colored flakes most commonly schists and granite pegmatites. It can survive weathering, and form sparkling grains in sands and sandstone. Muscovite. From the mineral collection of …
Neotocite
Formula: (Mn,Fe,Mg)SiO3.H2O Amorphous Description: Neotocite forms black to brown resinous masses from the alteration of manganese silicates. DODGE COUNTY: Neotocite is tentatively identified as microscopic light yellow brown grains in the oolites of the Mayville iron formation …
Northupite
Formula: Na3Mg(CO3)2Cl Isometric Description: A rare carbonate mineral found in dry lake sediments and other unusual sedimentary environments. DODGE COUNTY: A grain 0.6 cm. long found in the matrix of the Mayville oolitic iron formation was tentatively …
Opal
Formula: SiO2.nH2O Amorphous Description: Opal is a mineraloid composed of spherical silica aggregates with various amounts of interstitial water. It forms under a wide range of low-temperature geological conditions. Opal may be deposited by silica secreting …
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 …