Blakeite

Chemical formula: Fe<sup>3+</sup><sub>2</sub>(Te<sup>4+</sup>O<sub>3</sub>)<sub>3</sub>

Blakeite is a very rare iron tellurite, forming microscopic, orange-red crystals in the oxidation zones of ore deposits.

## Characteristics Blakeite is a secondary iron tellurite, occurring as very small, tabular or prismatic crystals, rarely exceeding 0.1 mm. It forms aggregates in the shape of rosettes, coatings, or appears as single, scattered crystals. Its intense, orange-red to red color makes it easily noticeable despite its small size. ## Physical Properties Due to the microscopic size of its crystals, most physical properties of blakeite have not been precisely determined. Hardness is estimated at approximately 3 on the Mohs scale. Luster is described as vitreous to adamantine. It is a transparent to translucent mineral. ## Colors and Varieties This mineral occurs in characteristic shades from orange-red to red. No color varieties or commercial varieties are distinguished. ## History and Name Blakeite was first described in 1951 by Sidney A. Williams. The mineral is named in honor of Frank Blake (1894-1950), a chemist at the Arizona Bureau of Mines, who first synthesized this compound in the laboratory. The type locality (locus typicus) is the Baker mine in San Bernardino County, California, USA. ## Uses Blakeite has no industrial application. Its significance is purely scientific and collectible, as a very rare secondary mineral.

Properties

Mohs hardness
3
Luster
Vitreous to Adamantine
Streak
Light reddish brown
Density
4.96
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Blakeite is identified by its characteristic, intense orange-red color, vitreous or adamantine luster, and occurrence as microscopic, tabular crystals. Its environment of occurrence is key – oxidation zones of tellurium-rich deposits, where it coexists with other tellurites and tellurates. ## Distinguishing from Similar Minerals It can be confused with other secondary, red tellurium minerals, such as emmonsite or mackayite. Differentiation requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS), due to the microscopic size of the crystals. Its monoclinic crystal system distinguishes it from triclinic emmonsite. ## Crystal Forms Blakeite crystals are most often very small, with a tabular or short-prismatic habit. They often form radial aggregates, rosettes, or thin coatings and crusts on the surface of the host rock or other minerals.

Geological environment

## Genesis Blakeite is a secondary mineral, formed in the oxidation zones of hydrothermal ore deposits rich in tellurium. It forms under low temperature and pressure conditions as a result of the weathering of primary tellurides, mainly in dry and desert climates. ## Mineral Associations This mineral often coexists with other secondary tellurium minerals, such as emmonsite, mackayite, eztlite, rodalquilarite, as well as quartz, barite, hematite, and native gold. ## Localities The most important and well-documented blakeite localities worldwide include: - Baker mine (type locality) and Aga mine in San Bernardino County, California, USA. - Bambolla mine in Moctezuma, Sonora, Mexico. - Wendy mine in La Paz County, Arizona, USA.

Rarity

Very rare

For collectors

## Quality Criteria The quality of blakeite specimens is primarily assessed based on the richness and aesthetics of the microcrystals. Specimens with numerous, well-formed, intensely colored crystals forming rosette aggregates are most valued. The contrast with the rock matrix and the presence of rare associated minerals are also important. Due to their size, specimens are evaluated under a microscope. ## Popular Localities The best and most sought-after blakeite micromineral specimens by collectors come from historical localities in the USA (California, Arizona) and from the Bambolla mine in Mexico, which has yielded many world-class specimens of secondary tellurium minerals.

Care and storage

## Cleaning Blakeite specimens are extremely delicate and susceptible to mechanical damage. Cleaning should be limited to an absolute minimum. If necessary, compressed air (from a safe distance) can be used to remove loose dust particles. Any contact with water, chemicals, or brushes should be avoided. ## What to Avoid Contact with water and any liquids that could dissolve or damage the microscopic crystals must be strictly avoided. The mineral is sensitive to shocks, ultrasound, and sudden temperature changes. It should not be exposed to direct sunlight. ## Storage Specimens should be stored in stable conditions, in closed, padded "micromount" boxes that protect against dust, moisture, and mechanical damage. The best solution is display under glass or in specialized showcases for microminerals.

Sources

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