Formula: Mg3Si2O5(OH)4 Monoclinic, orthorhombic, hexagonal
Serpentine is a family of polymorphs that include the flaky to platy antigorite, massive lizardite and fibrous clinochrysotile, orthochrysotile and parachrysotile. The polymorphs are often intimately intergrown in a particular rocks, hence the localities for all the serpentine family minerals are combined below. Serpentine minerals form as the result of low grade metamorphic alteration of magnesium-rich minerals such as olivine, orthopyroxene and periclase. They are abundant rock-forming minerals in ultramafic rocks and their metamorphic equivalents which are often called serpentinites. They are also common in marbles. Green serpentine-rich rocks, particularly when veins with white carbonate or quartz forms the decorative stone called verd antique. Talc, chromite, chlorite and magnesite are commonly associated minerals.
ASHLAND COUNTY: Serpentine is described as an alteration product of olivine and other minerals in the Keweenawan gabbros exposed throughout the Gogebic Range in the county. It occurs as small grains with chlorite, iron oxides and zeolites (Van Hise and Irving, 1892).
IRON COUNTY: Serpentine is described as an alteration product of olivine and other minerals in the Keweenawan gabbros exposed throughout the Gogebic Range in the county. It occurs as small grains with chlorite, iron oxides and zeolites. (Van Hise and Irving, 1892).
KENOSHA COUNTY: Serpentine is a common secondary minerals in cores from a subsurface, diamond-bearing lamprophyre diatreme, discovered within the outskirts of Kenosha (Carlson and Adams, 1997.).
LINCOLN COUNTY: Serpentine is described as an alteration product of olivine in altered peridotite exposed in the bed of the Wisconsin River a short distance below its confluence with the Copper River, near Merrill (Irving, 1883).
MARATHON COUNTY: Massive serpentine as pseudomorphs after olivine occurs with talc in outcrops south of Rozellville, S 1/2 sec. 15, S 1/2 sec. 16, and NW NW SW sec. 22 T.26N. R.4E. (LaBerge and Myers, 1983).
— Serpentine occurs with talc along the Little Eau Pleine River in NE SE sec. 24 T.26N. R.3E. (LaBerge and Myers, 1983).
— Serpentine-rich rock occurs as float in the west 1/2 sec. 9 T.26N. R.7E. (LaBerge and Myers, 1983).
— Serpentine occurs with talc and actinolite in the NW sec. 10 T.27N. R.8E. (LaBerge and Myers, 1983).
— Serpentine cut by veins of calcite occur in a road cut along County A in the middle of the north edge of sec. 34 T30N R. 6E. (Brown, personal communication, 1995).
MARINETTE COUNTY: Serpentine occurs as felted fibrous masses in ultramafic rocks in SW NE and SE NW sec. 21 T.37N. R.21E. It is here associated with magnesite, talc and quartz ( report of E.J. Longyear, 1945, WGNHS files). Massive serpentine is also found in the NW NW sec. 22 T.37N. R.21E. (Schulz and LaBerge, 2003).
POLK COUNTY: Small fibers of chrysotile occur with calcite, tremolite and chlorite along joint surfaces in the Dresser Trap rock Company Quarry, sec. 5 and 6 T.33N. R.18W. (Cordua, 1989).
RUSK COUNTY: Antigorite occurs in metamorphosed iron formation, mafic tuffs and diabase dikes in the Eisenbrey massive sulfide deposit north of Ladysmith. Associated minerals include magnetite, anthophyllite and cordierite (May, 1996).
WOOD COUNTY: Serpentine occurs in a number of ultramafic bodies near Milladore and Rudolph. It is often as platy antigorite, intergrown with talc. and can be polished if found in large enough pieces. The ultramafic rocks were the subject of sporadic talc mining in the past.
— Serpentine occurs at the Trowbridge-Nott Mine north of Milladore (NW NW SW sec. 11 T.25N. R.5E) where it is found in talc schist and chlorite schist (Aldrich ,1928; Shaw, 1942; W. S. Cordua field notes).
— Serpentine occurs at the Something Mine (old Czaikowski Property) near Milladore (NE SW sec. 15 T.25N. R.5E.) It is found with talc, chlorite and other minerals (Aldrich,1928; Shaw, 1942; W. S. Cordua field notes).
— Antigorite occurs in drill core on the Jadacek Farm, N 1/2 NE sec. 18 T.25N. R.6E. (WGNHS files, 1963).
— Serpentine can be found in fields and excavations near Rudolph, particularly around Tower Hill. The serpentine occurs with calcite, tiny magnetite crystals, brucite, talc and, locally almandine. Some pieces can be cut and polished (Crowns, 1976; Buchholz, 1994, personal communication).