SEM photo of acicular fergusonite-(Y) crystals on block-like cheralite crystals. The fergusonite-(Y) crystals are a maximum of 100 microns long. From Summit Lake Mine, Stettin, Marathon County, Wisconsin. (Al Falster specimen and image.)

Formula: YNbO4. Tetragonal


Fergusonite-(Y) is a rare earth mineral found in granitic and other pegmatites. It may also be found in placer deposits from the weathering and erosion of such bodies.

MARATHON COUNTY: Tiny acicular crystals of fergusonite-(Y), approximately 100 microns long, are found in pegmatites cutting amphibole syenite in the Stettin area. These can be found growing on cheralite. (Falster et al., 2000).