Formula: (Y,Ce,Ca)(Ta,Ti,Nb)2(O,OH)6 Orthorhombic
Description: Tanteuxinite-(Y) forms brownish black resinous crystals and masses in granite pegmatites and placer deposits derived from them.
MARATHON COUNTY: Tanteuxinite was identified from pegmatites in the Koss pit, a rotten granite quarry several miles west of Wausau (Tom Buchholz, pers. com.)
Tiny grains of a mineral tentatively identified as a “tanteuxinite-like” mineral was reported from pegmatites at the Wimmer #3 pit, south of Rib Mountain, near Wausau. (Tom Buchholz, pers. com.).