Brookite Value, Price, and Jewelry Information

Dark red-brown, 0.87-ct brookite, 9.3 x 4.2 mm, rectangular step cut, Pakistan. © The Gem Trader. Used with permission.

Brookite

Brookite usually occurs in very dark colors, transparent only in small fragments. Cuttable crystals are exceedingly rare, making attractive faceted gems prized collector’s items.

Brookite Information

Data Value
Name Brookite
Crystallography Orthorhombic. Occurs only in crystals; tabular, prismatic, pyramidal; often striated.
Refractive Index 2.583-2.740
Colors Brown, yellow brown, reddish brown, dark brown to black; rarely blue.
Luster Adamantine to submetallic.
Hardness 5.5-6
Fracture Subconchoidal
Specific Gravity 4.14 normal; 3.87-4.14.
Birefringence 0.122–0.157
Cleavage Indistinct
Dispersion 0.131
Luminescence None.
Luminescence Present No
Transparency Transparent to opaque.
Formula TiO2
Pleochroism Strong: yellow-brown/ reddish-brown/ orange to golden brown. An hourglass-shaped zonal coloration is sometimes seen in bluish crystals.
Optics a = 2.583; β = 2.584; γ = 2.700–2.740. Biaxial (+).
Optic Sign Biaxial +
Etymology After the English mineralogists and crystallographer J.H. Brooke. Arkansite is named after the US state of Arkansas.
Occurrence In gneisses, schists, and sometimes in igneous rocks; contact deposits.
brookite crystal on quartz - Pakistan

Brookite crystal on quartz, Kharan, Balochistan, Pakistan. Photo by Géry Parent. Licensed under CC By-SA 3.0.

Comments

Brookite, anatase, and rutile are polymorphous minerals. They share the same chemical formula, TiO2 (titanium dioxide), but have different crystal systems and other gemological properties.

Although not a very rare mineral, brookite crystals typically form in thin tabular shapes. This makes cutting gemstones very difficult. Although brookites have dispersion that exceeds that of diamonds, their dark colors and possibly submetallic luster can mask their fire. Due to these factors, you’re more likely to find faceted brookites in gem collections than jewelry collections.

emerald-cut brookite - Pakistan

Brownish red, emerald-cut brookite, 0.52-ct, 6.5 x 3.8 x 1.5 mm, Kharan, Pakistan. © ARK Rare Gems. Used with permission.

Arkansite

A black, opaque, and bipyramidal brookite variety, arkansite occurs in the eastern Siberian region of Russia and Magnet Cove, Arkansas, USA.

arkansite (brookite) crystal

Arkansite, Magnet Cove, Arkansas, USA, on display at the Mineralogical Museum, Bonn, Germany. Photo by Ra’ike. Licensed under CC By-SA 3.0.

“Platinum Quartz”

Some quartz specimens from Brazil contain striking, “insectile” inclusions of brookite blades and rutile needles. These have been marketed as “platinum quartz.” The name most likely alludes to the metallic appearance of the inclusions, although they contain no platinum. (Please note that so-called “platinum aura quartz” refers to possibly diffusion-treated quartz, not the included material).

quartz with brookite inclusion - Brazil

Called “dragonflies in quartz” by Brazilians, some quartz crystals like this clear, polished specimen show spectacular insect-like inclusions of brookite. 5.2 x 2.8 x 2.8 cm. Diamantina, Jequitinhonha valley, Minas Gerais, Southeast Region, Brazil. © Rob Lavinsky, www.iRocks.com. Used with permission.

Identifying Characteristics

Brookite has over the limit (OTL) refractive indices of 2.583-2.740.

This gem shares some properties with another rarely faceted mineral, rutile. These fellow polymorphs have overlapping ranges of color and refractive index (RI). Nevertheless, rutiles usually have uniaxial optic character while brookites have biaxial. Rutiles also have heavier specific gravity (SG) than brookites.

brookite blade crystals - Russia

Inter-grown brownish red brookite blades, 3.6 x 2.3 x 0.2 cm, Dodo Mine, Puiva, Ural Mountains, Russia. © Rob Lavinsky, www.iRocks.com. Used with permission.

Synthetics

Scientists have synthesized brookite crystals hydrothermally for various projects and commercial applications, including research into its photocatalytic properties (like its fellow polymorph, anatase). However, there’s no known jewelry use for this lab-created material.

Enhancements

None known.

Sources

Pakistan produces beautiful crystals as well as cuttable material.

Other notable sources include the following:

  • United States: Magnet Cove, Arkansas (contact metamorphic rocks); California; Maine; Somerville, Massachusetts; Ellenville, New York (hydrothermal deposits); North Carolina.
  • United Kingdom: Dartmoor, England; Wales.
  • Minas Gerais, Brazil; France; Russia; Tirol, Switzerland (typical Alpine deposits).
brookite crystal - Wales, United Kingdom

A rich brown brookite crystal on druzy quartz and limestone matrix, 5.8 x 4.6 x 2.7 cm, Prenteg, Tremadoc, Wales, United Kingdom. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

Transparent stones always weigh less than 1-2 carats. Larger stones are opaque.

Care

Of the gem-quality titanium dioxide polymorphs, brookites have the best wearability since they have indistinct cleavage. However, they still have a hardness of 5.5 to 6, which makes them somewhat susceptible to scratching. Use protective settings for jewelry wear and store these gems separately from harder stones to avoid contact scratches. Avoid mechanical cleaning systems. Clean brookites with a soft brush, mild detergent, and warm water. For more care recommendations, consult our gemstone jewelry cleaning guide.

brookite in quartz - oval cut, Brazil

Quartz has much greater wearability as a jewelry stone than brookite. A Brazilian quartz with brookite inclusions like this oval-cut gem could be an excellent way to add brookite to your jewelry collection. 30.45 cts, 20.0 x 17.0 x 12.4 mm. © ARK Rare Gems. Used with permission.

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