Formula: UO2 Isometric
Description: Uraninite is a strongly radioactive mineral found in pegmatites, high temperature hydrothermal veins, and lower temperature ground water precipitates in reduced sedimentary environments and along unconformities. It is often altered to and intergrown with a number of other uranium-rich minerals.
FLORENCE COUNTY: Uraninite occurs in the lithium-rich pegmatites in Fern in T. 39N. R.17E. (Falster, 1992, pers. comm.).
FOREST COUNTY: A fragment of uranium-rich quartz pebble conglomerate was found near a lookout tower on McCaslin Mountain (Sec. 35 and 36 T.34N. R.16E.). Although the particular uranium-bearing mineral was not specified in the description, it is likely to consist in part of uraninite. (U.S.G.S., 1976).
-Small grains of uraninite were reported in several small pegmatites along state highway 55 south of Alvin. (T. Buchholz, 2003, pers. com.)
MARINETTE COUNTY: A strongly radioactive material was found by Banks and Cain (1969) as an accessory in the Newingham granodiorite on the north side of Hwy. 8, west of Pembine in the center of the north 1/2 of sec. 5 T.36N. R.20E. It was associated with zircon, titanite and clinozoisite. The material was translucent to opaque, yellow to yellowish brown and was coated with a black material, possibly uraninite. Banks and Cain speculate that the yellow to yellow brown mineral was a silicate analogous to thorite.
WAUPACA COUNTY: Local radioactive zones occur in the granite exposed at the “Anklam Prospect” approximately one mile NE of Big Falls on County Hwy G (south 1/2 sec. 23 and north 1/2 sec. 26 T.25N. R.12E). Samples collected ranged up to 0.08% U3O8. The uranium is in uraninite associated with fluorite (W.G.N.H.S. files; U.S.G.S., 1976).
- Sparsely disseminated uraninite occurs in veins and biotite clots at a mine claim near Dupont in SW sec. 17 and NE sec. 20 T.25N. R.13E. (W.G.N.H.S. files).
WOOD COUNTY: Sparsely disseminated uraninite occurs as anhedral grains in granitic rocks at the Mathy (a.k.a. Tork) Quarry on the north edge of Wisconsin Rapids (NE SW sec. 1 T.22N R. 5E.) (Tom Buchholz, pers. com).