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Exceptional Brookite on Calcite

The Mineral brookite




Brookite is one of the three main forms of titanium dioxide. It forms distinct and unique crystals, and is often associated with the two other minerals it is polymorphous with, Rutile and Anatase. Brookite almost always forms together with Quartz, and is occasionally entirely included within a Quartz crystal.

Brookite is named in honor of Henry J. Brooke (1771-1857), an English mineralogist who specialized in crystallography and discovered several new mineral species.
Chemical Formula TiO2
Composition Titanium dioxide
Color Reddish-brown, brown, yellow-brown, yellow-orange, greenish-gray, black. Often has lighter and darker color zones, or a black zone running through the center of a crystal.
Streak Light yellow-gray to nearly white
Hardness 5.5 - 6
Crystal System Orthorhombic
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
In characteristic flattened tabular or prismatic crystals with elongated pointed termination. These crystals may be standalone, or in platy aggregates or bladed. Crystals may also be bipyramidal or pseudohexagonal, as well as in equant stubby crystals. Crystals are usually microscopic to very small, except at a few localities where they occur in larger crystals. Crystals are usually  striated.
Transparency Transparent to translucent
Specific Gravity 4.1 - 4.2
Luster Adamantine, submetallic
Cleavage 3,2
Fracture Uneven, subconchoidal
Tenacity Brittle
In Group Oxides; Simple Oxides
Striking Features Crystal habits and luster
Environment In low temperature alpine Quartz veins and cavities in metamorphosed schists and gneiss, in hydrothermal vein deposits, and in placer deposits.
Rock Type Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


Brookite AUCTIONS

VARIETIES
 -  Brookite from Magnet Cove, Arkansas, with a characteristic color and shape.
POLYMORPHS
Rutile
Anatase


USES
Brookite is a rare collectors mineral and is desired by collectors, especially good crystals.

NOTEWORTHY LOCALITIES
A classic British locality is Twll Maen Grisial, Prenteg, Wales, the type locality for Brookite that was once well-known for producing large Brookite crystals. Other European localities include Le Trient, Wallis, Switzerland; the Reuss Valley, Uri, Switzerland; and Mt. Bregaceto, Borzonasca, Italy.

Exceptionally large and beautifully colored Brookite crystals come from Balochistan, Pakistan, at Taftan, Dalbandin, and Kharan. In Russia, well-formed crystals come from Siberia at the Dodo and Puiva Mine, both in Saranpaul. Large crude crystals have been found at Fitampito, Iralamavory, Madagascar.

In the U.S., the only significant Brookite locality is Magnet Cove, Hot Springs Co., Arkansas, which is famous for its large black and often lustrous crystals.

COMMON MINERAL ASSOCIATIONS
Quartz, Calcite, Titanite, Albite, Axinite, Rutile

DISTINGUISHING SIMILAR MINERALS
Topaz - Harder, not usually in flattened crystals.


brookite PHOTOS
 
ADDITIONAL RESOURCES
 
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