Formula: C HEXAGONAL
Graphite occurs primarily in metamorphic rocks where it forms by the deterioration of organic compounds during metamorphism. It thus can be found in schists, marbles and quartzites that form from the metamorphism of sedimentary rocks. Most of the Wisconsin graphite is fine-grained sooty material intergrown with other minerals in various metamorphic rocks.
ASHLAND COUNTY: “Graphitic materials” are reported associated with the iron formation in the Gogebic Range. Associated minerals are actinolite, magnetite, chlorite, biotite and quartz (Van Hise and Irving, 1982; Van Hise and Leith, 1911).
FLORENCE COUNTY: Graphite is reported as a fine-grained component of the Michigamme Slate throughout the county (Dutton, 1971). – Graphite is a fine-grained component of the Dunn Creek slate where it is associated with chlorite and pyrite. It is well-exposed at the Florence Mine in Sec. 20 and 21 in T.40N R.18E. It is also exposed in Sec. 17, 20, 21, 34, and 35 in T.40N R.18E and in Sec. 22, 26, 27, 34 and 35 in T.40N R.17E (Dutton, 1980).
— Graphite is found in drilling core through meta-sedimentary rocks in the Bass Lake area, east of Fence in T.38N R.17E (Nielsen, 1984).
FOREST COUNTY: Fine-grained graphite is found in the argillaceous rocks of the footwall zone in the Crandon deposit (May and Schmidt, 1982).
IRON COUNTY: “Graphitic materials” are reported associated with the iron formation in the Gogebic Range. Associated minerals are actinolite, magnetite, chlorite, biotite and quartz (Van Hise and Irving, 1892; Van Hise and Leith, 1911).
MARATHON COUNTY: Small veins and streaks of graphite in pegmatite cutting quartz syenite was observed near Wausau (Weidman, 1907b).
MARINETTE COUNTY: Graphite forms up to 5% of the fine-grained schists on Miscauno Island, east of Pembine. Here it is associated with quartz, muscovite, biotite and hematite (Depangher, 1982).
— Found in clastic meta-sediments and iron formation associated with the Duval massive sulfide deposit, Sec. 2 and 3 T.35N R.18E and Sec. 28 T.36N R.18E (Hollister and Cummings, 1982).
PORTAGE COUNTY: A weathered poorly crystalline graphitic material was mined in the early 1900’s from “shaley zones” in quartzite in T.25N R.6E near Junction City. Chalcopyrite was associated (Weidman, 1907b). The mine site is 1 mile of route 10 along County G. Drill core from near the old mine contained coarsely crystalline graphite interbedded with chert, iron formation and pyritic metavolcanic rocks (1990, Bruce Brown, WGNHS, personal communication).
VILAS COUNTY: Graphite schist is reported from near Manitowish (Dutton and Bradley, 1070).