May 28 2014
Brookite was named after Henry James Brooke (1771–1857), an English crystallographer and mineralogist.
Properties of Brookite
The following are the key properties of brookite:
- Cell Data
- Space group: Pcab
- a = 5.4558
- b = 9.1819
- c = 5.1429
- Z = 8
- Crystal Data
- Orthorhombic
- Point group: 2/m2/m2/m
- As crystals, to 12cm, typically tabular on {010} and elongated and striated || [001] rarely tabular on {001}
- Commonly pyramidal {111} or pseudohexagonal with {120} and {111}
- Twinning: On {120}, uncertain
- X-ray powder pattern: 3.51 (100), 2.900 (90), 3.47 (80), 1.893 (30), 1.662 (30), 2.476 (25), 1.691 (20)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
| TiO2 |
98.59 |
98.77 |
| Fe2O3 |
1.41 |
1.48 |
| Total |
100.00 |
100.25 |
- Optical Properties
- Optical Class: Biaxial (+)
- Pleochroism: very weak; yellowish, reddish, orange to brown
- Orientation: Z = b
- Dispersion: r > v, very strong, with crossed axial dispersion
- Absorption: Z >Y >X
- α = 2.5831 β = 2.5843 γ = 2.7004 2V(meas.) = 0° – 28°, variable with wavelength
- Estimated Properties
| Electron density |
Bulk density (electron density) = 3.92 g/cm3
note: Specific gravity of brookite = 4.12 g/cm3 |
| Photoelectric |
PEBrookite = 10.03 barns/electron
U=PEBrookite x ρ electron density = 39.34 barns/cm3 |
| Fermion index |
Fermion index = 0.07
Boson index = 0.93 |
Radioactivity
|
Brookite is not radioactive
|
How to Identify Brookite
Brookite can be identified in the field by its color variations, such as brown, light brown, dark brown, dark reddish-brown, and orange. Its transparent to translucent to opaque form has {120} an indistinct cleavage. This mineral has a sub-metallic luster with yellowish-white streak. The fracture on this mineral is sub-conchoidal.
The density of brookite is 4.1 to 4.14 g/cm3 with a hardness of 5.5 to 6 - between a knife blade and orthoclase.
Global Distribution
Brookite is distributed in the following places:
- Wales - At Fron Oleu, near Tremadog, Gwynned
- Switzerland - In the Maderanthal and Griessertal, Uri, at Salvan, Valais
- Austria - Found near Pragraten and Virgen, Tirol
- France - From Bourg d’Oisans, Isere
- Norway - From Hardangervidda
- Russia - At Atliansk, near Miass, Ilmen Mountains, Southern Ural Mountains, and large crystals in the Dodo mine, about 100km west-north-west of Saranpaul, Subpolar Ural Mountains.
- Italy - at Monte Bregaceto, near Genoa, Liguria
- Brazil - In the diamond placers of Bahia and Diamantina, Minas Gerais
- USA - At Magnet Cove, Hot Spring Co. Arkansas; Ellensville, Ulster Co. New York; and near Powderhorn, Gunnison Co. Colorado
Occurrence of Brookite and Useful Mineral Association
Brookite occurs in an accessory mineral in alpine veins in gneiss and schist; in contact metamorphic zones and hydrothermal veinlets; and in a common detrital mineral.
It is often associated with minerals such as anatase, rutile, titanite, chlorite, orthoclase, hematite, calcite, quartz, and muscovite.
References