Anatase Value, Price, and Jewelry Information


Anatase
By Didier Descouens (Own work) [CC-BY-3.0], via Wikimedia Commons

Anatase is usually found in very small crystals, seldom transparent, and even then very dark-colored. Gems have been cut as curiosities, but are almost never seen for sale on the market because of scarcity.

Anatase Value

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Anatase Information

DataValue
NameAnatase
Alternate Common NamesOctahedrite, oisanite.
Crystallography Tetragonal; crystals pyramidal, striated; also tabular and prismatic.
Colors Black, red-brown, brown, blue, deep indigo-blue; colorless to grayish, greenish, blue-green, lavender, pale yellow, yellow brown. Banding due to zonal growth often visible.
Luster Adamantine, sometimes slightly metallic.
Fracture Subconchoidal. Brittle.
Hardness 5.5-6
Specific Gravity 3.82-3.97
Birefringence 0.046 – 0.067
Cleavage Perfect 2 directions.
Dispersion 0.213 (o); 0.259 (e)
Luminescence None
Transparency Transparent to translucent. Pyramidal crystals or gems with dark tones may appear almost opaque.
Absorption Spectrum Not diagnostic.
FormulaTiO2
Pleochroism  Strong in deeply colored crystals: brown/yellow-brown/greenish-blue.
Optics = 2.534 – 2.564; e = 2.488-2.497. Uniaxial (-). See "Identifying Characteristics" below.
EtymologyFrom the Greek anatasis for “extension,” since the anatase “octahedron” is really a tetragonal bipyramid and, thus, elongated with respect to the octahedron of the isometric system.
OccurrenceGneisses, schists, and other metamorphic rocks; as detrital grains, as an accessory mineral in granites, and in various other igneous rocks.

Comments

Optics: = 2.534 – 2.564; e = 2.488-2.497. Uniaxial (-).

Refractive indices are extremely variable, depending on temperature and wavelength. Anastase is sometimes biaxial with small 2V (dark-colored crystals). 

Occurrence: Gneisses, schists, and other metamorphic rocks; as detrital grains, as an accessory mineral in granites, and in various other igneous rocks.

California: Gunnison County, Colorado; Arkansas; Massachusetts; Virginia; North Carolina.

Canada; Brazil; Cornwall, England; Wales; Norway; France; Italy; USSR.

Switzerland: gem material from the Alpine regions.

Brazil: found in diamondiferous gravels.

Comments: Anatase is usually found in very small crystals, seldom transparent, and even then very dark-colored. Gems have been cut as curiosities, but are almost never seen for sale on the market because of scarcity.

Name: Greek anatasis, meaning erection because the “octahedron” of Anatase is really a tetragonal bipyramid and elongated with respect to the octahedron of the isometric system.