Anatase crystal, 1 mm tall. From the Nine Mile pluton, near Wausau, Marathon County, Wisconsin. (Photo by Dan Behnke.)

Formula: TiO2 Tetragonal


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.

Anatase crystal, about 1 mm high, Nine Mine Pluton, near Wausau, Marathon County, WI. (Photo and specimen by Al Falster.)

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.).

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

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).

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