Pseudobrookite

(repeating unit)Fe₂TiO₅IMA symbolPbrk^[1]Strunz classification4.CB.15Crystal systemOrthorhombicCrystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)Space groupBbmmUnit cella = 9.81 Å, b = 9.95 Å,
c = 3.73 Å; Z = 8IdentificationColorDark reddish brown, brownish black, blackCrystal habitPrismatic to needle like, striatedCleavageDistinct on {010}FractureUneven to subconchoidalMohs scale hardness6LusterAdamantine, greasy, metallicStreakBrownDiaphaneityOpaque, transparent in thin splintersSpecific gravity4.33–4.39Optical propertiesBiaxial (+)Refractive indexn_α = 2.350 n_β = 2.390 n_γ = 2.420Birefringenceδ = 0.0702V angleMeasured: 50°References^[2][3][4]

Pseudobrookite is an iron titanium oxide mineral with formula: Fe₂TiO₅^[2] or (Fe³⁺,Fe²⁺)₂(Ti,Fe²⁺)O₅.^[3]

Discovery and occurrence

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.^[2]

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.^[4]

It occurs associated with hematite, magnetite, bixbyite, ilmenite, enstatite-ferrosilite, tridymite, quartz, sanidine, topaz, spessartine, beryl, mica, cassiterite and apatite.^[4]

Occurrences include:^[4]

• Mayen in the Eifel district, Germany
• Mont Dore, Puy-de-Dome, France
• Vesuvius, Italy
• Jumilla, Murcia Province, Spain
• Faial and São Miguel Islands, Azores
• Kilimanjaro, Tanzania;
• Reunion Island
• the Thomas Range, Juab County, Utah
• Crater Lake and Lemolo Lake, Oregon
• the Black Range, Sierra County, New Mexico
• Cerro los Remedios, Durango, Mexico

References