Markcooperite

Chemical formula: Pb<sup>2+</sup><sub>2</sub>(U<sup>6+</sup>O<sub>2</sub>)Te<sup>6+</sup>O<sub>6</sub>

Markcooperite is a very rare uranyl lead tellurate, forming microscopic, tabular crystals of an intense orange color.

## Characteristics Markcooperite is a secondary mineral from the uranyl tellurate group, occurring as extremely small, tabular or bladed crystals that rarely exceed 0.2 mm. It forms thin crusts and coatings on the host rock. Its most characteristic features are its intense, bright orange color and a strong, vitreous to slightly adamantine luster. ## Physical Properties Due to the microscopic size of the crystals, many physical properties, such as hardness or density, have not been precisely measured. The mineral is transparent to translucent. It exhibits strong pleochroism in shades from pale yellow to orange. ## Colors and Varieties Markcooperite occurs in a uniform, characteristic bright orange color. No color varieties or commercial names are known. ## History and Name The mineral was described in 2016 by Stuart J. Mills and co-workers. Its name honors Mark A. Cooper (born 1954), a Canadian crystallographer from the University of Manitoba, for his contributions to mineralogy and crystal chemistry, including research on tellurates. ## Uses Markcooperite, as an extremely rare mineral occurring in microscopic quantities, has no industrial applications. It is of purely scientific interest and is a coveted object for specialized collectors of rare minerals and micromounts.

Properties

Luster
Vitreous to sub-Adamantine
Streak
Orange
Cleavage
Perfect on {010}
Fracture
Irregular/Uneven
Transparency
Transparent to Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of markcooperite is based on its unique characteristics: bright orange color, form of microscopic, tabular crystals, and co-occurrence with other secondary tellurium and uranium minerals in the oxidation zones of deposits. Definitive identification requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other brightly colored, secondary uranyl minerals, such as becquerelite or curite. "Hand" distinction is practically impossible. However, markcooperite is distinguished by its chemical composition (presence of tellurium) and specific geological environment. From similar uranyl tellurates, it is distinguished by its characteristic orange color and triclinic crystal system. ## Crystal Forms It forms very small, thin, tabular crystals with hexagonal or rhombic outlines, often flattened. It occurs as individual crystals dispersed on the matrix or forms small, rosette-like aggregates and coatings.

Geological environment

## Genesis Markcooperite is a secondary mineral, forming in the oxidation zones (gossans) of hydrothermal ore deposits rich in gold and silver tellurides. It forms as a result of the weathering of primary minerals containing tellurium, lead, and uranium under strongly oxidizing conditions. ## Mineral Associations It most commonly co-occurs with other rare secondary minerals. In the type locality (Bambolla mine), it was found in association with quartz, barite, cerussite, choloalite, dugganite, jensenite, ottoite, parakhinite, and xocolatlite. ## Localities The only confirmed occurrence of markcooperite in the world is its type locality - the Bambolla (Bambollita) mine near Moctezuma in Sonora State, Mexico. This is one of the world's most important sites for secondary tellurium minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity and microscopic size, any authentic, well-documented specimen of markcooperite is valuable. The most highly prized specimens are those where the crystals, despite their small size, are well-formed, have an intense color, and form rich aggregates on a small piece of host rock. Contrast with the matrix and the presence of associated minerals also increase aesthetic and scientific value. ## Popular Localities The only source of specimens is the Bambolla mine in Mexico. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically, mainly circulating among specialized micromount collectors.

Care and storage

## Cleaning Markcooperite specimens should not be cleaned mechanically or chemically. Any attempts at cleaning can irreversibly damage the delicate, microscopic crystals. If dust removal is necessary, a gentle stream of compressed air can be used from a safe distance. ## What to Avoid Contact with water, acids, detergents, and other chemicals must be strictly avoided. The mineral is brittle and sensitive to shocks and temperature changes. As a uranium mineral, it is radioactive and should be handled with appropriate precautions, avoiding dust inhalation and direct skin contact. ## Storage Specimens should be stored exclusively in specialized, airtight "micromount" containers that protect them from mechanical damage, dust, and moisture. Store away from other minerals that could be damaged by radiation.

Sources

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