Images
Formula: TiO2
Simple oxide, paramorph of anatase and
rutile
Crystal System: Orthorhombic
Specific gravity: 4.08 to 4.18 measured, 4.133 calculated
Hardness: 5½ to 6
Streak: White to greyish white or yellowish white
Colour: Brown, yellowish brown, reddish brown; dar brown to iron-black; yellowish brown to dark brown in transmitted light
Solubility: Insoluble in acids (Dana)
Common impurities: Fe3+,Ta,Nb
Environments:
Metamorphic environments
Hydrothermal environments
Brookite is found principally in fissures and open cavities in
gneiss and
schist, in veins of the Alpine cleft type. It is also
found in contact metamorphic
zones, and it is a common detrital mineral
(HOM).
Associated minerals include anatase,
rutile, titanite,
orthoclase, albite,
quartz, hematite,
calcite, chlorite
and muscovite
(Dana, HOM).
Rutile may be epitaxial on brookite
(Mindat).
At Saint-Pierre-de-Broughton, Quebec, Canada, brookite occurs in
stilpnomelane
schist, as a mid- to late-stage mineral in Alpine
fissures, preceded by or contemporaneous with anatase.
Some crystals are partially coated with chamosite
(R&M 86.6.501-502).
At the type locality, Twll Maen Grisial, Gwynedd, Wales, UK, brookite is found in a hydrothermal vein
associated with quartz,
chamosite and albite
(Mindat).
At the Ellenville lead mine, Ulster county, New York, USA, brookite occurs on
quartz with galena
and chalcopyrite
(Dana).
At Somerville, Massachusetts, USA, brookite occurs in
quartz-calcite
veinlets in mafic rocks with
anatase, titanite and
rutile
(Dana).
At the Santa Nino mine, Santa Cruz county, Arizona, USA, brookite is associated with
quartz and K-feldspar variety
adularia
(R&M 87.2.126).
Back to Minerals