Formula: NiAs Hexagonal Description: Nickeline, also referred to as “niccolite”, is a rare mineral found in high temperature hydrothermal deposits, especially those in mafic igneous rocks. Other nickel minerals, pyrrhotite and chalcopyrite are commonly associated. ASHLAND …
Douglas County
Augite
Formula: (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6 Monoclinic Description: Augite is the most common mineral in the pyroxene family. It has many varieties due to the variation in chemistry possible in its complex coupled solid solution series. Augite is common in gabbroic …
Epidote
Formula: Ca2(Al2Fe3+)(Si2O7)(SiO4)O(OH)2 Monoclinic Description: Epidote is a common mineral formed during low grades of metamorphism and hydrothermal activity. It is particular common in metamorphosed basalts and gabbros where it replaces plagioclase, pyroxene and olivine. It can also …
Laumontite
Formula: CaAl2Si4O12.4H2O Monoclinic Description: Laumontite is a member of the zeolite family and occurs most frequently in veins and amygdule fillings in basaltic rocks. The mineral forms as the rocks are subjected to heating during relatively …
Tetrahedrite-tennantite
Formula: (Cu,Fe,Ag,Zn)12(Sb,As)4S13 Isometric Description:Tetrahedrite forms a solid solution series with tennantite and freibergite in moderate to low temperature hydrothermal deposits. DOUGLAS COUNTY: Irving (1882) reports finding tetrahedrite in “small quantities in traverse veins in copper-bearing rocks”. This occurrence …
Phillipsite
Formula: (K,Na,Ca,Ba)4-7(Al4-7Si12-9)O32.12H2O Monoclinic Description: White phillipsite-K crystals on matrix. From Nickel Quarry, Oberwiddersheim, Hungen, Volgelsburg, Hesse, Germany. Specimen is 4.5 x 4.5 x 2 cm in size. (Photo courtesy Dan and Diana Weinrich Minerals; unauthorized reproduction is …
Calcite
Formula: CaCO3 HEXAGONAL Description: Calcite sceptor crystals from Shullsburg, Wisconsin. UW–River Falls specimen. Sample is about 8 cm high. (Photo by Pete Rodewald.) Calcite is an abundant mineral found in many geological environments. It forms by precipitation from …
Copper
Formula: Cu Isometric Description: Copper wire on gossan, Flambeau Mine, Ladysmith, Rusk County, WI. The wires are a few mm long. (Photograph and specimen by Pete Rodewald) Native copper occurs as veins and cavity fillings in hydrothermally …
Potassium Feldspar
Formula: KAlSi3O8 Monoclinic or Triclinic Description: Potassium feldspar refers to any of the three polymorphs microcline, orthoclase or sanidine. The distinction between these minerals can be made with certainty only after detailed X-Ray analysis. This has not …
Apophyllite Series
Formula: KCa4Si8O20(F,OH).8H2O Tetragonal Description: Apophyllite series minerals form from low temperature hydrothermal fluids. It is particularly common in veins within gabbros and basalts. DOUGLAS COUNTY: White to pink cleavage masses and crude platy crystals several centimeters across …