Rutile - TiO2

Named in 1800 by Abraham Gottlob Werner from the Latin "rutilus", meaning "reddish, Rutile is a mineral composed primarily of titanium dioxide, TiO2. Rutile is the most common natural form of TiO2. Two rarer polymorphs of TiO2 are known:

• Anatase (sometimes known by the obsolete name "octahedrite"), a tetragonal mineral of pseudo-octahedral habit
• Brookite, an orthorhombic mineral

The Rutile structure is the usual atomic arrangement for AX2 compounds with moderate-sixe cations. Each cation (Ti4+) is surrounded by six O2- ions in slightly deformed octahedral coordination and each O2- is bounded to three cations in triangular coordination. Rutile is basically TiO2 but forms some degree of solid solution with Tapiolite Fe(Nd,Ta)2O6. Fe2+, Fe3+, Ta5+ and Nb5+ may be present in rutule as major constituents.

Rutile is more common than other TiO2 polymorph, it is dense, high-temperature, high-pressure mineral that occur in both igneous (granite, syenite, pegmatite) and metamorphic rocks (Eclogite, marble)

Optical properties:
Color: Deep red-brown
Form: Usually more or less euhedral tetragonal crystals with square or octagonal section. It also occur as acicular hair-like inclusions in quartz or biotite.
Interference colors: Masked by mineral colors
Relief: High


Bibliography



• Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen
• E. WM. Heinrich (1956): Microscopic Petrografy. Mcgraw-hill book company,inc




Photo
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Rutile crystals (high Relief and deep red-brown colors). PPL image. 2x (Field of view = 7mm)
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Rutile crystals (high Relief and deep red-brown colors). PPL image. 2x (Field of view = 7mm)
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Rutile crystals (high Relief and deep red-brown colors). PPL image. 2x (Field of view = 7mm)