PYROCHLORE GROUP (Ce, Ca, Y)2(Nb,Ta)2O6(OH,F) Isometric

Description: Pyrochlore is a group of rare minerals found in pegmatitic granites, syenites, and carbonatites.

MARATHON COUNTY: Pyrochlore group mineral can be found as tiny grains in the Stettin Pluton and Nine-Mile Granite in the Wausau area. Numerous locations, many as ephemeral construction sites, are reported in Buchholz, Falster, and Simmons (2009).

- Octahedral ceriopyrochlore crystals up to 3 mm in diameter were found in a pegmatite dike in the SW NW sec. 22 T.29N. R.6E. This material was originally described as "marignacite." The crystals were light to yellow brown. Associated minerals were lithium-rich mica, quartz, K feldspar, fluorite, rutile, aegirine, riebeckite, and zircon (Weidman and Lenher, 1907). Small yellow ceriopyrochlore crystals still are found in the dumps at the nearby old thorium mine (Buchholz, 1994, personal communication).

- A pyrochlore group mineral is found at the Ladick Quarry (sec. 19 and 20 T. 27N. R.6E) (Buchholz Falster, and Simmons, 2002).

- A pyrochlore group mineral was tentatively identifed at the Koss Pit, a "rotten granite" quarry several miles west of Wausau (SW sec. 2 T27N R.5E) (Buchholz, Falster, and Simmons, 2000).

- A pyrochlore group mineral was identifed at the Red Rock North Pit, a "rotten granite" quarry along Spring Brook road west of Wausau (Buchholz , Falster, and Simmons, 2009).

- Tiny grains of uranpyrochlore have been found at the Wimmer #3 "rotten granite" quarry SW of Rib Mountain (Buchholz, Falster, and Simmons, 2009).

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