WGNHS
Wisconsin Geological and Natural History Survey

Xenotime-(Y)

Tiny yellow crystal of Xenotime-(Y) in cavity in granitic rock. Crystal is about 0.4 mm high. From Koss Pit, Marathon County, Wisconsin. Tom Buchholz specimen. (Photo by Dan Behnke.)

Formula: YPO4 Tetragonal

Description:

Xenotime-(Y) from the Nine Mile Pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo by Al Falster.)

Xenotime-(Y) is a rare accessory mineral generally found in complex pegmatites. It resembles zircon in physical appearance and may be mistaken for it. It is noticeably softer than zircon, however.

Xenotime-(Y) from the Nine Mile Pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo by Al Falster.)

MARATHON COUNTY: Xenotime-(Y) has been reported as yellow to brown crystals up to 1 mm in diameter in pegmatites of the Nine Mile pluton, such as are exposed in the “rotten granite” quarries south of Rib Mountain (sec. 19 and 20 T.28N. R.7E.) (Falster, 1987).
– Xenotime-(Y) has been reported in the pegmatites at Wimmer Pit #3, south of Rib Mountain. (NW sec. 19 T.28N R7E) (Buchholz, 1999b). It is fairly abundant, but difficult to distinguish from associated zircon.
– Xenotime-(Y) occurs as light brown to yellow xls. at the Koss Pit, (SW sec. 2 T27N R.5E) south of Rib Mountain. (Buchholz, Falster and Simmons, 1999).
– Xenotime-(Y) occurs at the Red Rock Granite North Pit (along Spring Brook Road) and the Ladick Quarry (sec. 19 and 20 T. 27N. R.6E.) (Buchholz and Simons, 2002).
– Xenotime-(Y) was found in an excavation for a house foundation, on the west side of 108th Avenue, Stettin. It was associated with siderite (replaced by iron oxides, brookite and zircon. (Tom Buchholz, 1997, pers. comm.).