Cliffordite

Chemical formula: U<sup>6+</sup>Te<sup>4+</sup><sub>3</sub>O<sub>9</sub>

Cliffordite is a very rare uranyl tellurate, forming tiny, yellow crystals with a strong adamantine luster.

## Characteristics Cliffordite is a very rare mineral from the oxide group, chemically a uranyl tellurate. It occurs as very small, isometric crystals, usually octahedral in shape, not exceeding 0.3 mm in size. These crystals often form aggregates and coatings. Due to its uranium content, cliffordite is a radioactive mineral. ## Physical Properties Cliffordite crystals are characterized by a strong, adamantine luster. They are transparent to translucent. The Mohs hardness is approximately 4, and the density is high, around 6.46 g/cm³. ## Colors and Varieties This mineral has a characteristic bright yellow color, sometimes with a greenish tint. No varieties are distinguished. ## History and Name Cliffordite was discovered in the Bambolla (Bambollita) gold mine in Moctezuma, Sonora State, Mexico. It was described in 1966 by Joseph A. Mandarino, E.J. Graff-Petersen, and S.A. Williams. The mineral is named in honor of Clifford Frondel (1907-2002), Professor of Mineralogy at Harvard University, for his contributions to uranium mineralogy. ## Uses Cliffordite has no industrial applications. It is of purely scientific and collector's interest as a very rare uranium mineral.

Properties

Mohs hardness
4
Luster
Adamantine
Streak
Light yellow
Density
6.46
Cleavage
None
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Cubic

Diagnostic features

## Identification Cliffordite can be identified by its bright yellow color, isometric, octahedral crystals, and very strong, adamantine luster. A key diagnostic feature is its high radioactivity, which can be measured with a Geiger counter. ## Distinguishing from Similar Minerals It can be confused with other yellow secondary uranium minerals. Differentiation from similar uranium tellurates and tellurites, such as mackayite or schmitterite, requires advanced analytical methods like X-ray diffraction (XRD). ## Crystal Forms Crystals are very small, usually below 0.3 mm. They have an isometric habit, most often forming octahedra {111}.

Geological environment

## Genesis Cliffordite is a secondary mineral formed in the oxidation (weathering) zones of hydrothermal gold-tellurium deposits. It forms in arid, desert climates as a result of the alteration of primary tellurides. ## Mineral Associations It most commonly co-occurs with quartz, barite, emmonsite, mackayite, schmitterite, native gold, and other tellurides and tellurates. ## Localities The most important and type locality is the Bambolla mine in Moctezuma, Sonora State, Mexico. This is the only confirmed locality from which well-formed specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a cliffordite specimen depends on the size and development of the crystals and their abundance on the rock matrix. Specimens with visible, sharp crystals of intense yellow color, contrasting with a quartz matrix, are most valued. Due to the microscopic size of the crystals, specimens are evaluated as "microminerals." ## Popular Localities The only source of collector specimens is the historical type locality – the Bambolla mine in Mexico. Material from this location is extremely rare on the market.

Care and storage

## Cleaning Due to radioactivity and the small size of the crystals, mechanical cleaning is inadvisable and usually unnecessary. Any manipulation of the specimen should be done with caution. ## What to Avoid Avoid skin contact, inhalation of dust, and ingestion due to the toxicity and radioactivity of uranium. Do not heat the specimen. Store away from radiation-sensitive materials. ## Storage Cliffordite specimens must be stored in specialized, lead-lined containers or thick plastic boxes, away from areas of permanent human occupancy. The container must be clearly marked as radioactive material. Storage within a specialized collection of radioactive minerals is recommended.

Sources

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