Formula: TiO2 Tetragonal
Description: Rutile is an accessory mineral found in a wide variety of rocks, usually as tiny grains. As such it occurs in such rocks as granite, syenite, schist, gneiss, amphibolite, marble and eclogite. It also occurs as a “heavy mineral” in sediments because of its high density and relative chemical stability. Although there are few reported occurrences in Wisconsin, it is likely locally abundant. Tyler (1940) for example reported rutile as tiny “foxy red” to brown grains as a widespread accessory mineral in the Precambrian rocks in the Lake Superior region.
FOREST COUNTY: Rutile is a “heavy” mineral in the McCaslin quartzite exposed in Forest and adjacent Langlade, Marinette and Oconto Counties (Olson, 1964).
JUNEAU COUNTY: Tiny yellow-gold sprays of rutile occur in and on quartz at the Necedah Bluff Quarry (NE sec. 24 T.18N. R.3E.) (Greenberg et al., 1986; Buchholz, 1994, personal communication).
MARATHON COUNTY: Rutile occurs abundantly in the pockets of the pegmatites of the Nine Mile Pluton, such as are exposed in the “rotten granite” quarries south of Rib Mountain. Here it occurs as “sagenite aggregates” averaging 1 mm. in diameter showing a variety of colors including black, yellow, olive green and reddish brown. (Falster, 1987). Buchholz (1999b) describes a vuggy pegmatite containing abundant “plates of silvery-colored reticulated twins (sometimes grading into black)” from the Wimmer #3Pit, south of Rib Mountain. Rutile also is found in the granites at the Koss Pit several miles further west. A niobium-bearing rutile, previously called Ilmenorutile, is found as granular to blocky black micro-crystals in pegmatites at the Koss Pit several miles west of Wausau. (Buchholz, Falster and Simmons, 1999, 2000)
— A niobium-bearing rutile, previously called Ilmenorutile is found as granular to blocky black micro-crystals in pegmatites at the Wimmer #3 Pit (SW sec. 2 T.27 N. R.5E.) SW of Rib Mountain. (Buchholz, and Simmons, 2002) and as black micro-crystals in pegmatites at the LaDick Pit east just east of Hwy 107, north of Highway 153. (Buchholz, Falster and Simmons, 2000)
— Rutile is a very rare late stage mineral in 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).
— Rutile is reported as an accessory mineral in a pegmatite in the Stettin Pluton exposed in the NW sec. 22 T.29N. R.6E. west of Wausau. Here it is associated with quartz, K feldspar, lithium-rich mica, riebeckite, aegirine, fluorite, pyrochlore and zircon. (Weidman, 1907).
RUSK COUNTY: Rutile is reported at the flambeau Copper Mine near Ladysmith. (Jone, Jones and LaBerge, 1999)
SAUK COUNTY: Rutile occurs as a microscopic “heavy” mineral in the Baraboo Quartzite (Becker, 1931).
WOOD COUNTY: Micro-xls. and masses of rutile occur in quartz at the Tork and Haessley quarries near Wisconsin Rapids. Associated minerals are anatase, titanite and brookite (Buchholz, 1996).