WGNHS
Wisconsin Geological and Natural History Survey

Chromite

Chromite with pen for scale. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, courtesy of the U.S. Geological Survey Denver Library Photographic Collection. (Photo by Andrew Silver.)

Formula: FeCr2O4 Isometric

Description:

Chromite occurs as small grains in ultramafic rock associated with serpentine, talc, magnesite and brucite. It is an important ore of chromium when found in quantity.

CLARK COUNTY: A minute black metallic grain in amphibolite at the Long Branch Quarry west of Thorpe, was identified as chromite according to EDS data (Buchholz, 2000, personal communication).

MARINETTE COUNTY: Octahedral grains up to 3 mm. in diameter are associated with serpentine, talc and magnesite in the SW NE and SE NW Sec. 21 T.37N R.21E east of Pembine (W.G.N.H.S. files, 1945 report from E.J.Longyear Co.). Chromite also occurs as small grains in serpentinite in the NW NW sec. 22 T.37N. R.21E. (Schulz and LaBerge, 2003).

WOOD COUNTY: Chromite grains occur as small grains in talc in drill core taken from SE SE NW Sec. 8, T.23N R.6E, near Rudolph (W.G.N.H.S. files,1985).
— Chromite occurs as microsocpic octahedral crystals in vugs in a mafic dike cutting granite in the County Quarry, in Cary township (NW sec. 1 T. 23N R.2E). (Tom Buchholz, personal communication).