Formula: KAl2(AlSi3)O10(OH,F)2 Monoclinic
Description: Muscovite is a common mica, forming silvery to pale-colored flakes most commonly schists and granite pegmatites. It can survive weatheirng, and form sparkling grains in sands and sandstone.
ADAMS COUNTY: Muscovite in common in quartzite and granitic rocks at Hamilton Mounds, Sec. 31 T.20N. R.7E and sec. 36 T.20n. R.6E.) (Greenberg et al., 1986).
CHIPPEWA COUNTY: Occurs along bedding planes and in argillites interbedded with the Flambeau quartzite, as exposed in SE sec. 1, SW sec. 2 and NE NE sec. 11 T.32N. R.7W. and in the SE SW sec. 6 T.32N. R.6W. (Campbell, 1981).
CLARK COUNTY: Found in felsic phyllonite with quartz and K feldspar exposed below the Mead Dam (SE sec. 29 T.27N. R.3W.) north of Willard (Myers, 1977; WGNHS outcrop descriptions).
— Major mineral in kink-banded muscovite-chlorite schist and muscovite quartzite exposed in a small quarry along Co. M in NE sec. 1 T.26N. R.4W., N of the South Fork of the Eau Claire River (Myers, 1977; WGNHS outcrop description).
DODGE COUNTY: Flakes of greenish to pink muscovite occur in pegmatites cutting quartzite in the Michels Materials Waterloo Quarry, NE sec. 33 and NW sec. 34 T.9N. R.13E. (Buchholz et al., 2003). Some of the pink muscovite is lithium enriched. (Buchholz et al., 2005b)
EAU CLAIRE COUNTY: Muscovite is found in a pink pegmatite dike near the County K Bridge over the Eau Claire River at SW NW sec. 19 T.27N. R.8W. (Myers et al., 1974).
FLORENCE COUNTY: Muscovite (variety fuchsite) is an accessory in the altered pegmatites at the Payant-Chrissman molybdenite prospect pits in sec. 33 T.38N. R.19E, south of Aurora. It occurs with biotite, pyrite and chalcopyrite, as well as molybdenite (Greenberg, 1983).
— Small books and cluster of silvery to greenish yellow muscovite up to 4 mm. in diameter occur in the complex pegmatites in sec. 22 and 29 T.39N. R.17E. They occur with K feldspar, quartz, lepidolite, tourmaline, columbite-tantalite and other rare minerals (Koehler, 1988, 1989).
FOREST COUNTY: Sericite is abundant in the altered volcanic rocks of the Crandon massive sulfide deposit near Little Sand Lake. (Lambe and Rowe, 1989).
IOWA COUNTY: Muscovite in the form of sercite is formed locally in the mineralized zone of the Demby-Weist mine, SW sec. 21 T.7N. R.4E., near Pleasant Ridge. It is here found as “pearly white flakes, scales and silky tufts” associated with galena, sphalerite, marcasite and smithsonite in silicifed Cambrian and Ordovician dolomite, limestone and sandstone (Heyl, et al., 1959). This mineral is likely widepsread, but overlooked, in many of the deposits of the Upper Mississippi Valley zinc-lead district thoughout Iowa, Lafayette and Grant Counties.
JUNEAU COUNTY: Fine-grained muscovite is a common component of the brecciated quartzite in the quarries of Necedah Bluff, NE sec. 24 T.24N. R.3E. (Greenberg, et al., 1986).
MARATHON COUNTY: Muscovite is a common constituent of the granites of the Wausau Complex (Falster, 1987) Ninemile complex near Wausau (Patton et al., 1989) and Mosinee (Anderson et al., 1980). Buchholz (1999b) reports abundant pale green muscovite locally in a pocket in a pegmatite in one of the “rotten granite” quarries south of Rib Mountain.
MARINETTE COUNTY: Muscovite is found in granite at the Camp Five Molybdenite deposit, north central part of sec. 18 T.33N. R.20E., near Middle Islet. (Fisher, 1965).
RUSK COUNTY: Sericite occurs in the altered volcanic rocks of the Flambeau massive sulfide deposit near Ladysmith. (May, 1977).
SAUK COUNTY: Fine grained sericite is common in the Baraboo Quartzite and Baxter Hollow Granite (Gates, 1942).
WAUPACA COUNTY: Muscovite occurs in the granite quarried in Waupaca (SW sec. 20 T.22N. R.12E.) (Greenberg, et al., 1986).
WOOD COUNTY: Tiny euhedral crystals of muscovite occur in pockets with fluorite, calcite and K feldspar at the Frederick Schill Quarry, near Vesper on the E side of HWy. 182. (Buchholz, 1999).
— Fuchsite occurs in tiny grains within the quartzite quarried southwest of Veedum in S 1/2 sec. 7 and N 1/2 sec. 18 T.22N. R.3E. This mineral gives the quartzite a pleasant green color. (Greenberg et al., 1976).
— Sericite is common in the quartzite quarried in SW NE sec. 2 T.23N. R.4E. near Sherry (Greenberg et al., 1986).
— A lithium-rich muscovite occurs along joint-surfaces wirh chlorite, siderite and other minerals at the Cary Rock Road Quarry, NE sec. 4, T23N R2E. (Buchholz,1997).
— Muscovite is a common constitutent of the argillite and quartzite found in quarries and roadcuts near Power’s Bluff, NE NE sec. 5 T.23N. R.4E. and SE NE sec. 32 T.23N. R.4E. (Greenberg et al., 1986)
— Muscovite occurs as xl. rosettes and flakes along shears in granite at the Haske Quarry, Cary Bluffs, Sec. 25 T.24N. R.2E. (Buchholz, 1997, personal communication).