Formula: (Fe,Mn)(Nb,Ta)2O6 Orthorhombic
Description: Columbite-tantalite refers to a group of minerals having varying amounts of iron, manganese, niobium, and tantalum. They are found as platey black grains in complex granitic pegmatites.
DODGE COUNTY: Tiny prismatic crystals of manganocolumbite and manganotantalite were seen 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, 2005b).
FLORENCE COUNTY: Small platey crystals and sprays usually 1-2 mm across and occasionally up to 1 cm in diameter are commonly associated with albite, spodumene, and other minerals in the complex pegmatite dike swarm in Fern Township. Such pegmatites are widely exposed in Sec. 22 T.39N. R.17E (Kohler, 1988, 1989). Columbite-tantalite is also found as crystals up to 2 cm long in a pegmatite in the NE SW SE Sec. 29 T.39N R.17E (Koehler, 1989, personal communication). Some of this material has been shown to be manganocolumbite and manganotantalite (Falster et al., 1995).
MARATHON COUNTY: Falster (1987) notes small stubby black crystals of columbite-tantalite rimmed by an unknown yellow mineral in a few pockets in the Wausau pluton, such as exposed in the granite quarries south of Rib Mountain.
— Ferrocolumbite, ferrotantalite, manganotantalite, manganocolumbite, and tantalum-bearing ferrocolumbite have been found at the Koss pit, at the Wimmer #3 pit south of Rib Mountain, and at the Red Rock Granite North Pit (Buchholz, Falster, and Simmons, 1999; Buchholz and Simmons, 2002; and Buchholz and others, 2004).
— Well-formed crystals up to 4 mm of “mostly manganoan tantalian ferrocolumbite” were found in granite in the Maguire Pit, part of the Ladick East quarry complex along State Highway 153 east of Wausau (Buchholz and others, 2005a).
— Ferrocolumbite and manganotantalite are reported from the Ladick quarry, sec. 19, T.24N R5E (Buchholz et al., 1999).
— Road construction in 2011 in Stettin township revealed several small vuggy pegmatites with interesting mineralogy. Anorthoclase, microcline, and albite are the main rock-forming minerals. Associated minerals are zircon, columbite-(Fe), ilmenite, brookite, cassiterite, pyrochlore-group minerals, pyrite, arsenopyrite, and fluorite (Buchholz, Falster and Simmons, 2012).
SHAWANO COUNTY: Tiny crystals of columbite-tantalite a few millimeters across are found in the complex pegmatite exposed south of the Tigerton Dells near Tigerton in the NE 1/4 SW 1/4 NE 1/4 Sec.15 T.26N R.12E. Associated minerals include gadolinite, allanite, beryl, and phenakite (WGNHS files, 1986).
WOOD COUNTY: Tiny crystals of ferrocolumbite a few millimeters across are found in the granite at Haske Quarry, sec. 25 T.24N. R.2E. (Buchholz and others, 2005a).