Formula: Ca2(Mg,Fe)5Si8O22(OH)2 Monoclinic Description: Actinolite is a common member of the amphibole family. It typically forms during low-grade metamorphism of mafic igneous rocks (such as basalt and gabbro) or carbonate-rich rocks such as limey mudstones. ASHLAND COUNTY: Van …
Ashland County
Allanite
Formula: (Ce,Ca,Ce,La,Nd,Y)2(Al,Fe)3(Si2O7)(SiO4)O(OH) Monoclinic Description:Allanite refers to a group of minerals found as an accessory in a number of different rocks such as syenite, granite and gneiss. It may also be a component of granite pegmatite. It …
Almandine
Formula: Fe3Al2(SiO4)3 Isometric Description: Almandine is a common garnet found in a many metamorphic rocks such as schist, gneiss, amphibolite and iron formation. It is commonly associated with micaceous minerals such as muscovite, biotite and chlorite and …
Andalusite
Formula: Al2SiO5 Orthorhombic Description: Andalusite is found in phyllites, schists and gneisses and associated quartz veins. It indicates relatively low pressure metamorphism of aluminum-rich rocks, such as shales. ASHLAND COUNTY: Andalusite occurs as “chiastolite” in fine-grained schists outcropping …
Ankerite
Formula: Ca(Fe,Mg,Mn)(CO3)2 Hexagonal Description: Ankerite is formed as a sedimentary precipitate, a groundwater and hydrothermal precipitate and by metamorphic recrystallization of iron-rich sedimentary rocks. ASHLAND COUNTY: Ankerite is a component of the Ironwood iron formation in the Penokean …
Apatite Group
Formula: Ca5(PO4)3(F,Cl,OH) Hexagonal Description:Apatite denotes a family of minerals referred to variously in older literature as “fluorapatite,” “chlorapatite,” “carbonate-apatite” or “hydroxlyapatite” and in newer literature as apatite- (CaF) etc. depending on which anion group dominates. Members …
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 …
Biotite Group
Formula: K(Mg,Fe)3(Al,Fe3+)Si3O10(OH,F)2 Monoclinic Description: Biotite refers to a group of common rock-forming minerals forming a series between phlogopite and annite. The name is best used as a field name for dark micas for which the exact composition …
Bornite
Formula: Cu5FeS4 Orthorhombic Description: Bornite forms as a primary hydrothermal precipitate or a later supergene replacement mineral. It occurs with other copper minerals such as covellite, malachite and azurite. It is marked by its intense purple to …
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 …