Wimmer Pit #3
COUNTY: Marathon TOPO. QUAD.: Wausau West 7 1/2' Quad
LOCATION: Large "rotten granite" quarry south of Rib Mountain. Productive through the 1990's.
ACCESSIBILITY: Quarry, now completely reclaimed (2004). Other granite quarries in the region continue to produce interesting arrays of rare minerals, usually as micros. Collecting by permission only.
View of the Wimmer pit #3, showing the "rotten granite" with less weathered core stones. Quarry is south of Rib Mountain, near Wausau, Marathon County, Wisconsin.
GEOLOGY: Weathered granitic rocks of the Nine Mile Pluton, cut by complex pegmatites and aplite dikes. Lots of mariolitic cavities occur in the granites and pegmatites.
Anatase - black, blue or green bipyramidal micro-xls alter to leucoxene
Apatite - clear to white tabular to elongated micro-xls.
Bavenite - Rare elongated yellow micro-xls, often coated with clay. May form jackstraw aggregates.
Bertrandite - Rare as clear to cloudy blocky twined micro-crystals.
Beryl - rare as tiny clear or bluish crystals.
Brookite - Common as prismatic green, yellow, brown, blue or black micro-xls.
Cheralite -Ce- Bipyramidal micro-crystals, often coated with reddish clayey material.
Fluorite - etched white, grey, purple or, rarely, green massive material
Garnet - reddish to off-white xls., locally found.
Goethite - Massive, or golden brown acicular xls. in altered siderite.
Hematite - common as platey micro-xls.
Ilmenite - black tabular micro-xls.
Ilmenorutile - Free-growing slender xls. in vugs, bearing significant amounts of Nb, and some Ta.
Monazite - Ce, Nd and La varieties.
Phenacite - clear transparent xls., rarely up to 1 inch long. Some twinned.
Plagioclase - Small xls. of white albite are reported.
Potassium Feldspar - Coarse cleavable massive and euhedral xls., sometimes etched. both microcline and sanidine occur. Some colors are pink, red, white or, rarely, green. Fluoresce deep red.
Quartz - massive; some vugs bear large clusters of white, clear or smoky quartz, locally doubly terminated. Many minerals,(hematite, chlorite, sphlaerite ,rutile etc.) are reported as inclusions.
Rhabdophane Group - intergrown with cheralite and monazite
Rutile- Twinned, single or reticulated groups of black, grey or silvery white.micro-crystals
Siderite Large xls. often altered to iron oxides. Smaller, less altered xls. may be found in quartz.
Synchysite/ parisite - Brownish micro-xls.
Xenotime (?) Reported as brownish, yellow to clear tetragonal micro-xls.
Zircon - Common as white to yellow micro-xls.
BIBLIOGRAPHIC REFERENCES: Thomas Buchholz, 1999 "Minerals of a Wausau Pegmatite, Marathon County, Wisconsin", Rocks and Minerals, vol .74 #4, p. 254 - 258.
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