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



• Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., & Lameyre, J. (2002). Igneous rocks. A classification and glossary of terms, 2. Cambridge University Press.
• Middlemost, E. A. (1986). Magmas and magmatic rocks: an introduction to igneous petrology.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.




Photo
rutilo0035(2).jpg

Rutile crystals (high Relief and deep red-brown colors). PPL image. 2x (Field of view = 7mm)		 rutilo0035(3).jpg

Rutile crystals (high Relief and deep red-brown colors). PPL image. 2x (Field of view = 7mm)		 rutilo0035(4).jpg

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