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Gemstones 250x250

The Mineral anatase

Large Anatase in Albite

Anatase is a relatively uncommon yet very aesthetic form of titanium dioxide. It forms distinct and unique crystals, which are usually microscopic to very small, though a few localities have produced larger crystals. Anatase is polymorphous with the more common Rutile, as well as Brookite. It is often replaced entirely by Rutile, forming interestingly shaped Rutile pseudomorphs after Anatase. The name Anatase is derived from the Greek word anatasis, which means elongation, in allusion to its elongated crystal habit (in relation to Rutile.)

Chemical Formula

TiO2

Color

Dark blue, navy blue, black, reddish-brown, brown, honey yellow, orange. Rarely red, green, or gray. Occasionally in two colors or in lighter and darker color splotches or zones.

Crystal System

Tetragonal

Properties

Streak
White
Hardness
5.5 - 6
Transparency
Transparent to translucent
Specific Gravity
3.8 - 3.9
Luster
Adamantine, submetallic
Cleavage
1,4
Fracture
Subconchoidal
Tenacity
Brittle

Crystal Habits

As steeply formed dipyramidal crystals, or in clusters of such crystals. Crystals may have sharp pointed terminations, or they be modified or partially flattened. Also pseudo-octahedral, tabular, in highly modified complex crystals, in scepter-formed habits, and in rounded waterworn crystals. Crystals are usually heavily striated cross-wise, and may have interesting tapering and accordion-like growths. X-shaped twins do exist but are very rare.

Additional Information

Composition
Titanium dioxide
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, as well as placer deposits.
Rock Type
Metamorphic

Varieties

 -   Octahedrite is a synonym of Anatase, but often is specifically referring to well-shaped, sharp pseudo-octahedral or dipyramidal forms of Anatase.
 -   Yellow, earthy Anatase pseudomorph after Titanite.

Uses

Anatase is a rare collector's mineral and is highly desired by collectors, especially when in good crystals.

Noteworthy Localities

Europe contains some of the best localities for Anatase. Exceptionally large dark crystals come from Matskorhae and Dyrfonni, in Hardangervidda, Norway. In France, two important Anatase localities are Bourg d'Oisans, Isère, Rhone; and La Madeleine pass, Savoie. Good crystals are well-known from several regions in Switzerland, specifically the Binntal, Wallis; the St. Gotthard Massif, Ticino; and Tujetsch (Tavetsch), Grischun. The Italian Alps also contains many Anatase localities where well-formed tiny crystals have been found, especially in the Val d'Ossola, Piedmont. A classic British locality is Twll Maen Grisial, Prenteg, Wales.

Well formed, lustrous Anatase crystals have come from a newer find in Kharan, Balochistan, Pakistan. Minas Gerais, Brazil, has several important localities, where large crystals come from Diamantina, in the Jequitinhonha valley; the Cuiabá District, Gouveia; and in scepter-shaped formations in Dattas.

In the U.S., Anatase localities include the Lot Mine, Gunnison Co., Colorado; the Yates Brooks Farm, Lattimore, Cleveland Co., North Carolina; the County Line Quarry, Wrightsville, York Co., Pennsylvania; and Somerville, Middlesex Co., Massachusetts. Large crystals and interesting pseudomorphs have come from the the Jones Mill Quarry and Perovskite Hill, Magnet Cove, Hot Spring Co., Arkansas.

Common Mineral Associations

Quartz, Orthoclase, Albite, Axinite, Hematite, Titanite, Talc, Chlorite, Rutile, Brookite

Distingushing Similar Minerals

Babingtonite - Different crystal habits, lacks any transparency.
Sphalerite - Different crystal habits, lower hardness.
Zircon and Spinel- Much harder.
Sapphire - Much harder, forms in hexagonal crystals.
Xenotime - May be very difficult to distinguish.


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