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A mineral form of titanium dioxide, TiO2, having characteristic orthorhombic crystals and a red-brown to black color.

[After Henry James Brooke (1771-1857), British mineralogist.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Minerals) a reddish-brown to black mineral consisting of titanium oxide in orthorhombic crystalline form: occurs in silica veins. Formula: TiO2
[C19: named after Henry J. Brooke (died 1857), English mineralogist]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
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References in periodicals archive ?
Other rarer polymorphs of TiO2 are known including anatase, akaogiite, and brookite. Titanium dioxide (TiO2) is the standard white pigment used principally in paints, paper, and plastics.
We used seven different Ti[O.sub.2] structures: Polyethylene glycol (PEG)-amorph Ti[O.sub.2], amorph Ti[O.sub.2], PEG-brookite, rutile, anatase, amorph bovine serum albumin (BSA), and brookite BSA.
Brookite titania [26] or hydrate titania [27] peaks at 59.2 and 60.6 may be due to titania and acid presence in the sol.
Jolivet, "Synthesis of brookite Ti[O.sub.2] nanoparticles by thermolysis of Ti[Cl.sub.4] in strongly acidic aqueous media," Journal of Materials Chemistry, vol.
It is noteworthy that no extra peaks corresponding to rutile or brookite phase were observed [12, 13].
Well-known phases of Ti[O.sub.2] are anatase, rutile, and brookite. Rutile is a tetragonal (a = 4.5937 [Angstrom], c = 2.9587 A), anatase is also a tetragonal (a = 3.7845 [Angstrom], c = 9.5143 [Angstrom]), and brookite is an orthorhombic crystal (a = 5.4558 [Angstrom], b = 9.1819 [Angstrom], c = 5.1429 [Angstrom]).
Ti[O.sub.2] can be associated with presence of rutile, which is the most common mineral of titanium dioxide; however, polymorphs rarely include brookite and anatase, both form unique and distinctive crystals on the earth, and this is typical in felsic rocks [20].
This compound have three crystalline phases: rutile (tetragonal structure), anatase (octahedral structure), brookite (orthorhombic structure), which according to the requirement of the electrostatic valence rule, each oxygen atom is shared by three octahedra.
Ti[O.sub.2] is a well-known semiconductor and a versatile compound that exists in three crystalline forms, anatase, rutile, and brookite [14, 21], which can only be activated with UV light due to its high band gap energy (3.0 eV for rutile phase and 3.2 eV for anatase phase).