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Spray of pseudobrookite needles from Topaz Mountain in Utah (size: 2.7 x 2.0 x 1.6 cm)
Category Oxide mineral
(repeating unit)
Strunz classification 4.CB.15
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Bbmm
Unit cell a = 9.81 Å, b = 9.95 Å,
c = 3.73 Å; Z = 8
Color Dark reddish brown, brownish black, black
Crystal habit Prismatic to needle like, striated
Cleavage Distinct on {010}
Fracture Uneven to subconchoidal
Mohs scale hardness 6
Luster Adamantine, greasy, metallic
Streak Brown
Diaphaneity Opaque, transparent in thin splinters
Specific gravity 4.33–4.39
Optical properties Biaxial (+)
Refractive index nα = 2.350 nβ = 2.390 nγ = 2.420
Birefringence δ = 0.070
2V angle Measured: 50°
References [1][2][3]

Pseudobrookite is an iron titanium oxide mineral with formula: Fe2TiO5[1] or (Fe3+,Fe2+)2(Ti,Fe2+)O5.[2]

Discovery and occurrence[edit]

Pseudobrookite was first described in 1878 for an occurrence in Uroi Hill (Arany Hill), Simeria, Hunedoara County, Romania. The name is from Greek ψευδής, for false, and brookite because of its misleading similar appearance to brookite.[1]

Pseudobrookite forms as pneumatolytic deposition and alteration within titanium-rich volcanic rocks such as andesite, rhyolite or basalt. It may be associated with xenoliths contained in the volcanics. It also commonly occurs in lithophysae.[3]

It occurs associated with hematite, magnetite, bixbyite, ilmenite, enstatite-ferrosilite, tridymite, quartz, sanidine, topaz, spessartine, beryl, mica, cassiterite and apatite.[3]

Occurrences include:[3]