Greenish mass of chamosite between two brassy pyrite masses in chert. Field of view is about 0.5 cm. From Bonita, San Diego County, California. (Photo by W. Cordua.)
Formula: (Fe,Mg)5Al(AlSi3O10)(OH)8 Monoclinic
Description: Chamosite is a member of the chlorite group found in iron-rich sedimentary rocks and in low-grade metamorphic rocks derived from them.
ASHLAND COUNTY: Chamosite is a common component of the banded iron formation of the Ironwood Formation throughout the Gogebic Iron Range (USGS, 1976; Schmidt, 1980).
FLORENCE COUNTY: Found as a component of the iron formation at several mines in T.40N R.18E near Florence (Dutton, 1971). These include the Florence Mine (Sec. 20 and 21), the Badger Mine (SE SE Sec. 34), and the Davidson Mine (NE SW Sec. 34).
IRON COUNTY: Chamosite is a common component of the banded iron formation of the Ironwood Formation throughout the Gogebic Iron Range (USGS, 1976; Schmidt, 1980).
Properties of minerals 