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: 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 commnuication).

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

- A pyrochlore group mineral was identifed at the Red Rock North pit, a "rotten granite" quarry along Spring Brook road west of Wausau. (Buchholz and Simons, 2002).

- Tiny grains of uranpyrochlore have been found at the Wimmer #3 "rotten granite" quarry SW of Rib Mountain. (Buchholz and Simons, 2002).

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