Formula: (Mg2)(Mg3Al2)(Al2Si6O22)(OH)2. Orthorhombic
Description: Gedrite is a member of the amphibole group. It forms during medium to high grade regional metamorphism of ultramafic, iron-rich or clay-rich protoliths.
JACKSON COUNTY: Gedrite has been reported intergrown with cummingtonite in the iron formation of the Jackson County Iron Mine, SE Sect. 15 T.21N. R.3W. (Kimball, 1979).
OCONTO COUNTY: Gedrite occurs as tiny grains in metavolcanic rocks near Mountain. (Sims et al., 1991).