Brookite
Current inventory:  1 gem
 

  
Brookite is named for Henry James Brooke (1771-1857), an English crystallographer and mineralogist.

Discovered in 1825; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

TiO₂

Titanium Oxide

Molecular Weight:

79.88 gm

Composition:

Titanium

59.94 %

Ti

100.00 %

TiO₂

Oxygen

40.06 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.15-10

Nickel-Strunz 10th Ed. ID:

4.DD.10

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
D : With medium-sized cations; frameworks of edge-sharing octahedra

Related to:

Polymorphous with Akaogiite, Anatase, Rutile, TiO2 II. Brookite is one of the five forms of titanium dioxide found in nature.

Varieties:

Arkansite

Synonyms:

Eumanite, Jurinite, Pyromelane

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

As crystals, to 12 cm, typically tabular and elongated and striated; commonly pyramidal or pseudohexagonal.

Twinning:

None

Physical Properties

Cleavage:

Poor/Indistinct on {120}, in traces on {001}

Fracture:

Irregular/Uneven, Sub-conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0

Density:

4.08 - 4.18 (g/cm³)

Luminescence:

White to grayish white or yellowish white

Radioactivity:

Not Radioactive

Optical Properties

Color:

Light to dark brown, Dark reddish brown, Red, Orange

Transparency:

Opaque to translucent, transparent in thin fragments

Luster:

Metallic adamantine to submetallic

Refractive Index:

2.583 - 2.741  Biaxial ( + )

Birefringence:

0.1220 - 0.1570

Dispersion:

0.131 (very strong)

Pleochroism:

Very weak; yellowish, reddish, orange to brown

Occurances

Geological Setting:

An accessory mineral in alpine veins in gneiss and schist; in contact metamorphic zones and hydrothermal veinlets; a common detrital mineral.

Common Associations:

Anatase, Rutile, Titanite, Orthoclase, Quartz, Hematite, Calcite, Chlorite, Muscovite.

Common Impurities:

Fe, Ta, Nb

Type Locality:

Twll Maen Grisial, Fron Olau, Prenteg, Gwynedd (Caernarvonshire), Wales, UK

Year Discovered:

1825

View mineral photos:

Brookite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Brookite is an extremely rare gem mainly because crystals are usually very dark colored and transparent only in small, thin fragments. Facet grade crystals are very small and rare and attractive faceted gems are among the rarest of all gems. Brookite is one of the three forms of Titanium Dioxide found in gemstones. The other two are Rutile and Anatase.

Brookite is a widespread mineral, but only a few localities afford fine crystals. At Fron Oleu, near Tremadog, Gwynned, Wales. From Bourg d’Oisans, Isère, France. In Switzerland, in the Maderanthal and Griessertal, Uri, at Salvan, Valais, and elsewhere. In Austria, found near Prägraten and Virgen, Tirol. From Hardangervidda, Norway. In Russia, at Atliansk, near Miass, Ilmen Mountains, Southern Ural Mountains, and large crystals in the Dodo mine, about 100 km west-northwest of Saranpaul, Subpolar Ural Mountains. In Italy, at Monte Bregaceto, near Genoa, Liguria. In Brazil, in the diamond placers of Bahia and Diamantina, Minas Gerais. In the USA, at Magnet Cove, Hot Spring County, Arkansas; Ellensville, Ulster County, New York; and near Powderhorn, Gunnison County, Colorado.
 

  
Brookite gems for sale: