Bastnaesite Series

Bastnaesite-(Nd) from block of miarolitic material collected in the County Materials Pit, on the north side of Townline Rd east of STH 107, Marathon County, WI. Collected July 29, 2007. Field of view is about 1.9 mm across. *(Specimen from Tom Buchholz, photo by Dan Behnke.)*

Formula: (Ce, La,Y, Nd)(CO₃)F Hexagonal

Description:

Bastnaesite in platey crystals from the Nine Mile pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. *(Photo by Al Falster.)*

The bastnaesite series is a group of minerals related by various degrees of substitute of the rare earth elements Ce, La, Nd and Y. These minerals are not common, but can be found in various granite pegmatites.

MARATHON COUNTY: Bastnaesite-Ce is found as red platy to coarse masses and crystals an few mm. in diameter in miarolitic cavities in pegmatites at the Koss Pit (SW sec. 2 T.27 N. R.5E.) SW of Rib Mountain. (Buchholz, Falster and Simmons, 1999, 2000). It is also found in similar conditions at the Wimmer Pit #3 south of Rib Mountain. The bastnaesite forms earthy patches masses that are difficut to recognize. (Buchholz and Simmons, 2002). Bastnaesite also 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).

Bastnaesite-(Ce) in complex rosette from the Nine Mile pluton near Wausau in Marathon County, Wisconsin. Scanning electron microscope image. (Photo by Al Falster.)

Bastnaesite occurs in cavities in granite at the County Materials Pit on the north side of Townline Rd east of STH 107, Marathon County, WI.

WAUPACA COUNTY: Bastnaesite group minerals were found as reddish-brown massess in road cuts in pegmatite cutting granite along County G near Keller Lake, NE of Big Falls. Associated minerals include euxenite-(Y), biotite, fluorite, K feldspar, allanite and various sulfides (Tom Buchholz, 2002, pers. com.).