WGNHS
Wisconsin Geological and Natural History Survey

Topaz

Tiny clear topaz crystal in cavity in granitic rock. Maguire Quarry, Marathon County, Wisconsin. Field of view is 0.9 mm left to right. (Dan Behnke specimen and image.)

Formula: Al2(SiO4)(F,OH)2 Orthorhombic

Description:

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

Topaz forms in granitic pegmatites, in cavities in rhyolitic volcanic rocks and in residual soils and placers derived from them.

PIERCE COUNTY: Small particles of topaz were reportedly found during placer mining operations for gold along Plum Creek within the confines of what is now Nugget Lake County Park. Diamonds, garnet and platinum were reportedly associated. (Colvin, 1977) .

MARATHON COUNTY: A water-worn pebble of clear topaz reportedly found in a gravel bar along the Wisconsin River near Wausau was examined by the author.

– Topaz has been found as tiny clear xls. up to 0.4mm in diameter and masses intergrown with albite in the McGuire Pit, part of the Ladick East quarry complex east of Wausau. Associated minerals include cassiterite, monazite and ferberite/hubnerite. (Buchholz et. al., 2004