Anatase

minerals

ilmenite

brookite

Images
Formula: TiO₂
Simple oxide, paramorph of brookite and rutile.
Specific gravity: 3.79 to 3.97
Hardness: 5½ to 6
Streak: White to pale yellow
Colour: Brown, pale yellow or reddish brown, indigo, black; pale green, pale lilac, grey, rarely nearly colourless; brown, yellow-brown, pale green, blue in transmitted light.
Solubility: Insoluble in acids (Dana)
Common impurities: Fe,Sn,V,Nb
Environments:

Igneous environments
Pegmatites
Carbonatites
Sedimentary environments
Metamorphic environments
Hydrothermal environments

Anatase is usually secondary, derived from other titanium-bearing minerals. In Alpine veins it is derived from the enclosing gneiss or schist by leaching by hydrothermal solutions. In also occurs in igneous and metamorphic rocks, in pegmatites and carbonatites. It is a common detrital mineral (HOM, Dana). Common associates include brookite, rutile, titanite, ilmenite, titanium-rich magnetite, hematite, quartz, K-feldspar variety adularia and chlorite (HOM, Mindat, Dana).

Localities

At the Mount Lyell Mines, Queenstown district, West Coast municipality, Tasmania, Australia, anatase is common in many disseminated ores and schistose wallrocks. Well formed crystals to 1 mm have been found on quartz crystals with abundant hematite inclusions (AJM 21.2.21).

At the Marcil quarry, near Ste-Clotilde-de-Châteauguay, Quebec, Canada, anatase has been found associated with quartz and dolomite. The mineral is formed early in the paragenetic sequence, appearing to have preceded quartz (R&M 86.6.549).

At the type locality, St Christophe-en-Oisans, Auvergne-Rhône-Alpes, France, anatase occurs in Alpine veins, derived from the enclosing gneiss or schist by hydrothermal solutions (Mindat).

At the the Santo Nino Mine, Santa Cruz County, Arizona, USA, anatase occurs in association with quartz, muscovite, muscovite variety sericite and K-feldspar variety adularia (R&M 87.2.126).

At Placerville, California, USA, anatase occurs with brookite on quartz (Dana).

At Quincy, Massachusetts, USA, anatase occurs in pockets in a pegmatite with aegirine, fluorite and ilmenite (Dana).

Near diabase dikes at Somerville, Massachusetts, USA, anatase occurs with brookite and titanite (Dana).

At Arvon, Buckingham county, Virginia, USA, anatase is found in joint planes in slate with quartz and pyrite (Dana).

The PT diagram below illustrates that rutile is stable at a higher temperature than anatase ( Journal of Materials Science, 46.855–874).























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