Pseudobrookite

Pseudobrookite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition [( Fe 3 ) 2Ti ] O5 and usually develops in the short to long prismatic crystals or radial- term, tufted mineral aggregates of up to 7 cm in size and reddish-brown to brownish black color.

Etymology and history

Was first found in 1878 on pseudobrookite Magura Uroiului at Uroi ( Arany ) in Romania Hunedoara County and described by Anton Koch (Hungarian: Antal Koch, 1843-1927 ), the ψευδ the mineral because of its similarity and likelihood of confusion with brookite after this with the Greek word addition ~ "false, spurious, fake " for named.

Classification

In the old classification of minerals according to Strunz ( 8th edition ) of the pseudobrookite belonged to the department of " oxides with the molar ratio of metal: oxygen = 2: 3 ," where he forms a separate, unnamed group together with Armalcolit and pseudorutile.

Since the 9th edition of the Strunz'schen Mineral classification of the departments Oxid-/Hydroxid-Klasse, however, are precisely divided by the size of the cations and partially renamed. Pseudobrookite is now available in the subdivision of " oxides with the molar ratio of metal: oxygen = 2: 3, 3: 5 and comparable and medium-sized cations ," where he is the unnamed group 4.CB.15 together with Armalcolit and Mongshanit.

The commonly used in English-speaking classification of minerals according to Dana sorted the pseudobrookite also in the class of oxides and hydroxides, there, however, in the department of " multiple oxides with different formulas ," where he along with Armalcolit and so far only with the System No.. IMA2000 -016 equipped the mineral unnamed subdivision 7.7.1 forms.

Education and Locations

Pseudobrookite forms as pneumatolytic decomposition product of ilmenite into titanium- rich andesites, rhyolites, basalts and other volcanics. In different paragenesis There he enters next ilmenite inter alia, with apatite, beryl, bixbyite, various mica, hematite, cassiterite, magnetite, quartz, sanidine, spessartine, topaz, tridymite.

So far pseudobrookite at around 130 localities (as of 2010) are detected, including in Algeria, Australia, Brazil, Bulgaria, Chile, Germany, France, Greece, Italy, Japan, Mexico, New Zealand, Norway, Austria, Romania, Russia, Slovakia, Spain, South Africa, Tanzania, the Czech Republic, Hungary, the United Kingdom ( UK) and the United States (USA).

Morphology

In general, show pseudobrookite crystals have a short to long prismatic habit with preferential growth direction along the b - and c- axis ( and ), resulting in the formation tafeliger crystals by {100 }, whose surfaces have a characteristic striation parallel to the c axis.

Crystal structure

Pseudobrookite crystallizes in the orthorhombic space group BBMM with the lattice parameters a = 9.77 Å; b = 9.95 Å and c = 3.72 Å and four formula units per unit cell.