Formula: TiO2 Tetragonal
Description: Anatase is a relatively rare mineral found in veins and cavities in schists, gneisses, granites, syenites and other related igneous rocks. It is also a product of weathering of other titanium minerals. Tyler (1940) notes anatase as a heavy mineral in “Huronian” meta-sediments as tiny yellow, light blue, colorless or yellowish euhedral grains and as tiny yellow euhedral grains in Keweenawan sediments.
MARATHON COUNTY: Black to, more rarely, yellow crystals about 1 mm. in maximum dimension are widespread in pockets in the Nine Mile pluton west and south of Wausau (Falster, 1984,1987; Falster et. al., 2000). It is usually a late stage mineral.
— Found in small black, blue and green xls. at the Wimmer Pit #3, south of Rib Mountain. Associated with zircon, ilmenite, fluorite and apatite in vugs in granite. Many show alteration to leucoxene (Thomas, Buchholz, 1993, pers. comm.).
— Found as dark tabular micro-xls. at the Koss Pit, south of Rib Mountain (Buchholz, Falster and Simmons, 1999).
Reported as occurring with brookite in a quarry on Mosinee Hill. (L. Brown, pers. comm.).
WOOD COUNTY: Sharp euhedral micro-xls. of orange to blue anatase occur with quartz and chlorite in veins in the Tork Company Quarry, Wisconsin Rapids (Thomas Buchholz, 1993, pers. comm.).
— Anatase as black microcrystals with deep blue highlights has been reported from quartz veins cutting granitic rock at the Frederick Schill Quarry, SW NW sec. 5 T.23N. R.4E. north of Vesper (Buchholz, 1999).