Brookite


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brookite

[′bru̇‚kīt]
(mineralogy)
TiO2 A brown, reddish, or black orthorhombic mineral; it is trimorphous with rutile and anatase, has hardness of 5.5-6 on Mohs scale, and a specific gravity of 3.87-4.08. Also known as pyromelane.

Brookite

 

a mineral of composition TiO2. Sometimes contains admixtures of iron and niobium. Layered structure, consisting of octahedral groups of TiO6, united by common ribs. Crystallizes in a rhombic system. The crystals are usually tabular, less frequently prismatic and dipyramidal. Their color is yellowish brown to reddish brown; their luster is adamantine or metallic. The hardness of brookite on the mineralogical scale is 5.5-6; density, 3,900-4,200 kg/m3. The crystals are found in gold placers and in alpine-type veins in the Urals (USSR); abroad the mineral is found in Switzerland, France, Austria, and the USA.

References in periodicals archive ?
Titanium dioxide pigment occurs in nature and is sourced from its ores: rutile, anatase and brookite. The titanium dioxide pigment is generally synthesized using the chloride and sulfite process.
Amorph, brookite, anatase, and rutile forms of Ti[O.sub.2] nanoparticles (Grafen Chemical Industries, Ankara, Turkey) were coated with PEG and BSA.
Titanium oxide is found in three different crystalline forms: rutile, anatase, and brookite. The anatase phase has been reported to display higher photocatalytic activity than the others, owing to its higher density of localized states [31].
It is well known that Ti[O.sub.2] has three polymorphs phases in nature: rutile, anatase, and brookite; the band gap of rutile phase and anatase phase are 3.0 eV and 3.2 eV, respectively.
While those of TiO2 powders are mainly from rutile phase (card number: 21-1276), followed by brookite (card number: 79-1973).
It is found in three crystalline phases: brookite (orthorhombic), anatase (tetragonal) and rutile (tetragonal), wherein the anatase and rutile phases are commonly used in photocatalysis, which the anatase phase is considered the highest catalytic activity (Linsebigler, Lu, & Yates, 1995).
(26.) Reyes-Coronado, D, Rodriguez-Gattorno, G, EspinosaPesqueira, ME, Cab, C, de Coss, R, Oskam, G, "Phase-Pure Ti[O.sub.2] Nanoparticles: Anatase, Brookite and Rutile." Nanotechnology, 19 763-770 (2008)
The molecular weight is 79.865, melting point 1843[degrees]C, Four naturally occurring titanium dioxide polymorphs exist : rutile, anatase, brookite and titanium dioxide .
The 'high-1' and 'good' reservoir quality (classes I and III, respectively) quartz sandstones from the E6 structure are mainly composed of quartz, with minor amounts of clay (illite and/or kaolinite) and carbonate cement forming minerals, admixture of feldspar and accessory minerals represented by pyrite, barite, anatase and/or brookite and zircon (Shogenov et al.
Ti[O.sub.2] crystallizes in three major structures: rutile (tetragonal), anatase (tetragonal), and brookite (rhombohedrical) (11).

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