Formula: (Fe,Mg,Zn)2Al9(SiO4)4(OH,O)2 Monoclinic
Description: Staurolite forms during the metamorphism of aluminous rocks at intermediate temperatures and pressures. It can form large euhedral crystals in schist, associated with muscovite, biotite, almandine and kyanite. Some crystals show distinctive cross or X-shaped twins.
IRON COUNTY: Staurolite occurs as porphyroblasts in schist associated with kyanite, almandine, biotite, quartz and oligoclase in a roadcut along Hwy 182 west of Powell (SE SW sec. 28 T.42N. R.4E.) (Mudrey, 1979). Another near-by outcrop in the NE NW sec. 23 T.42N. R.4E. is described by Sims (1985).
JACKSON COUNTY: Staurolite is found as anhedral grains 1 to 7 mm across in mica schists at the Jackson County Iron Mine, east of Black River Falls. (SE sec. 15 T.21N. R.3W.) Here it is associated with andalusite, almandine, biotite, muscovite and chlorite (Jones, 1978). Kimball and Spear (1984) describe two separate staurolite generations here with the first generation replaced by andalusite and the second generation replacing kyanite and andalusite.
LANGLADE COUNTY: Staurolite occurs in schist near Kempster where it is associated with andalusite, muscovite, quartz, garnet, plagioclase and chlorite (Geiger and Guidotti, 1989).
LINCOLN COUNTY: “Large euhedral staurolite porphyroblasts” are reported from “greywacke schist” with garnet and cordierite in the SE sec. 7 and NE sec. 18 T.31N. R.7E. near Merrill (Weidman, 1907b). Spear and Guidotti (1989) also report andalusite, muscovite, biotite, quartz and plagioclase as present in these rocks.
MARATHON COUNTY: Staurolite occurs with garnet in an outcrop along the Rib River in sec. 14 T.30N. R.4E. west of Hamburg (Weidman, 1907b).
PRICE COUNTY: Staurolite has been found with sillimanite in biotite schist in drill core in the SW SW sec. 26 T.39N. R.2W. and NW NE sec. 29 T.40N. R.1E. (Sims, 1989).
SHAWANO COUNTY: Staurolite mica schist was reported from the Menominee region in the northern part of the county by Irving (1883).
VILAS COUNTY: Staurolite was reported in drill core samples from a kyanite-bearing schist near Lac Vieux Desert (Allen and Barett, 1915).