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 …
Jackson County
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 …
Anthophyllite
Formula: (Mg,Fe)7Si8O22(OH)2 Orthorhombic Description: Anthophyllite is a mineral formed from the metamorphism of magnesium-rich rocks. It is often associated with other amphibole minerals, pyrope, and cordierite. JACKSON COUNTY: Anthophyllite occurs as long radiating fibrous crystals and masses intergrown …
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 …
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 …
Cacoxenite
Formula: AlFe24(PO4)17O6(OH)12.17H2O Hexagonal Description: Formed as an alteration of other phosphates. It occurs with minerals such apatite, dufrenite, and wavellite and with iron oxides such as goethite. It is an unusually attractive mineral, often forming small …
Chlorite Group
Formula: (Al, Fe, Li, Mg, MN, Ni, Zn)6 (Si, Al)4O10(OH, O)2 MONOCLINIC or TRICLINIC Description: Chlorite represents a group of over 10 minerals related by complex solid solution substitutions. These minerals are generally fine-grained, micaceous and dark green. …
Crandallite Group
Formula: CaAl3(PO4)2(OH)5.H2O Hexagonal Description: Crandallite is used here to refer to a group of minerals in the Crandallite group, including florencite. Crandallite itself is formed by groundwater precipitation in sedimentary rocks and soils as a result …
Cummingtonite
Formula: (Mg,Fe)7Si8O22(OH)2 Monoclinic Description: Cummingtonite is a member of the amphibole family. It commonly forms elongated to fibrous green to brown grains in metamorphosed iron-rich rocks. ASHLAND COUNTY: Cummingtonite is found in the Ironwood Iron Formation where it …