Formula: Mg3Si4O10(OH)2 Triclinic
Description:
Talc is found in magnesium-rich rocks, such as marbles or metamorphosed ultramafic rocks. It is commonly associated with other magnesium-rich minerals such as tremolite, serpentine and chlorite.
ASHLAND COUNTY: Talc is found as white platy grains in the Ironwood Iron Formation at the Berkshire Mine on Mt. Whittlesey (SW SE sec. 9 T.44N. R.2W.) Here it is associated with magnetite, quartz, chlorite, hematite, grunerite, almandine and plagioclase (Laybourn, 1979).
FLORENCE COUNTY: Talc is a component of greenstone and greenschist in the Michigamme Slate in sec. 28 T.39N. R.18E. where it is associated with actinolite and chlorite (Dutton, 1980).
IRON COUNTY: White to pink selvages of talc occur along rhodochrosite veins in the Montreal Mine, NE NE sec. 33 T.46N. R.2E. (Dickey, 1938).
JACKSON COUNTY: Masses of coarse foliated talc schist were abundant at the Jackson County Iron Mine, SE sec. 15 T.21N. R.3W. Associated minerals included coarse fibrous anthophyllite and cummingtonite and large subhedral almandine garnet crystals (Jones, 1978).
MARATHON COUNTY: Talc occurs at several places in the county in metamorphosed ultramafic rocks. Some localities given by LaBerge and Myers (1983) are:
— Massive talc with serpentine in outcrops in T.26N. R.4E. near Rozellville such as in S 1/2 sec. 15, S 1/2 sec. 16, sec. 21 and sec. 22.
— Massive talc with serpentine outcrop along the Little Eau Pleine River in SE SW sec. 24 T.26N. R.3E.
— Massive with serpentine and actinolite in the NW sec. 10 T.27N. R.8E.
MARINETTE COUNTY: Talc is associated with serpentine, magnetite and chromite in the SW NE and SE NW sec. 21 T.37N. R.21E. near Pembine. (1945, report from E.J. Longyear Co in W.G.N.H.S. files; Brown, 1976). Talc also occurs in serpentinite in the NW NW sec. 22 T.37N. R.21E. (Schulz and LaBerge, 2003).
ONEIDA COUNTY: Talc forms schist at the Lynne massive sulfide deposit (Kennedy, et al., 1991).
WOOD COUNTY: Talc was mined from a zone about 2 km. wide by 5 km. long trending NE-SW near Milladore. It was first worked by Native Americans. The sites are still visited by rockhounds seeking soapstone suitable for carving (Crowns, 1976).
— Talc schist and soapstone was mined at the Trowbridge-Nott mine in SW NW sec. 11 T.25N. R.5E. The talc is associated with serpentine, chlorite, brucite, pyrite, azurite, malachite, and octahedra of magnetite. (US Bureau of Mines, 1963, Shaw, 1942, Aldrich, 1928) Foliated talc with grunerite. Jackson County Iron Mine, near Black River Falls, WI (W. S. Cordua field notes).
— Talc schist and soapstone was mined at the Something Mine (also referred to as the old Czaikowski Property) in the NE SW sec. 15 T.25N. R.5E. The talc was associated with serpentine, chlorite, actinolite, tremolite, pyrite, and octahedra of magnetite. (U.S. Bureau of Mines, 1963, Shaw, 1942, Aldrich, 1928).
— Talc as soapstone occurs at the Toay test pit in the SE SE sec. 10 T.25N. R.5E. (WGNHS files).