WGNHS
Wisconsin Geological and Natural History Survey

Thorite

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Deep red thorite grains with potassium feldspar, quartz and zircon. Keller Lake pegmatites, Waupaca County, Wisconsin. Field of view is 2.0 mm left to right. Tom Buchholz sample. Dan Behnke image.

Formula: (Th,U)SiO4 Tetragonal

Description:Thorite is a rare mineral found in pegmatites and hydrothermal deposits.MARATHON COUNTY: Thorite is found in the pegmatites associated with the amphibole syenites of the Stettin pluton. Some grains and clusters may be several centimeters across. It is often altered to brownish thorogummite. (Falster, et. al., 2000).– Thorite occurs as tiny crystals at the Summit Mine, near the intersection of County O and County U near Stettin. (Tom Buchholz, 1995, pers. comm.).

– A thorite-like mineral was observed in the Red Rock Granite North Pit (along Spring Brook Road, southwest of Wausau. (Buchholz and Simons, 2002).

WAUPACA COUNTY: Thorite was reported as small reddish-brown crystals in altered biotite from road cuts in pegmatite cutting granite along County G near Keller Lake., NE of Big Falls. Associated minerals include euxenite-(Y), biotite, fluorite, K feldspar, bastnaesite group minerals, allanite and various sulfides. (Tom Buchholz, 2002, pers. com.)

WOOD COUNTY: Thorite is an accessory in the granite exposed in the Haske quarry in Sec. 25 T.24N. R.2E (Buchholz, et al, 2005a.).