Chadwickite

Chemical formula: U<sup>6+</sup>O<sub>2</sub>HAs<sup>3+</sup>O<sub>3</sub>

Chadwickite is an extremely rare uranyl arsenite, forming tiny, yellow crystals with a strong luster.

## Characteristics Chadwickite is a mineral from the arsenite group, chemically classified as a uranyl arsenite hydroxide. It occurs as very small, rarely exceeding 0.2 mm, rhombohedral crystals. It typically forms spherical aggregates or rosetted clusters. Its most characteristic visual feature is its intensely yellow color and very strong, almost adamantine luster. ## Physical Properties This mineral is characterized by a strong, adamantine luster. It is transparent. Due to its extreme rarity and microscopic crystal size, its hardness and density have not yet been precisely measured. ## Colors and Varieties Chadwickite occurs in a uniform, light yellow to canary yellow color. No color varieties or commercial varieties are known. ## History and Name The mineral is named in honor of Sir James Chadwick (1891–1974), a British physicist and Nobel Prize laureate in Physics in 1935 for his discovery of the neutron. It was officially approved as a new mineral species by the International Mineralogical Association (IMA) in 2020. The type material comes from the Duna mine in Russia. ## Uses As a mineral of microscopic size and extreme rarity, chadwickite has no industrial application. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals.

Properties

Luster
Adamantine
Streak
Light yellow
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Characteristic features of chadwickite include its intensely yellow color, strong adamantine luster, and occurrence in the form of tiny, spherical aggregates. A key diagnostic feature is its radioactivity. Its occurrence in association with other secondary uranium and arsenic minerals is also an important clue. ## Distinguishing from Similar Minerals Chadwickite can be confused with other yellow, secondary uranium minerals, such as uranophane, autunite, or torbernite. Due to the microscopic size of the crystals, reliable distinction from similar minerals is possible almost exclusively by advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Crystal Forms It forms very small, well-formed rhombohedral crystals. It is most commonly found as spherical or rosetted crystalline aggregates, growing on host rocks.

Geological environment

## Genesis Chadwickite is a secondary mineral, formed in the oxidation (weathering) zone of polymetallic, hydrothermal veins containing uraninite and arsenic minerals. ## Mineral Associations This mineral occurs in direct proximity to other secondary minerals. It is most often associated with arsenolite, metazeunerite, and uranophane. ## Localities The only confirmed locality of chadwickite in the world is its type locality – the Duna mine (Grube Duna), located within the Adun-Cholon ore field in the Transbaikal Territory, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of chadwickite is determined by the quality and development of the crystals, rather than their size. Specimens with clearly visible, sharp crystals forming aesthetic aggregates are most highly prized. The abundance of the mineral on the rock matrix and attractive associations with other rare minerals are also important. ## Popular Localities The only source of collector specimens is the Duna mine in Russia. Specimens from this locality are highly sought after by collectors specializing in mineral systematics and rare species.

Care and storage

## Cleaning Chadwickite specimens are extremely delicate and small. Mechanical or chemical cleaning is not recommended. The only safe method for dust removal is to use compressed air from a safe distance. ## What to Avoid Chadwickite is a uranium mineral, which means it is radioactive. It also contains arsenic, making it toxic. It is absolutely essential to avoid inhaling dust and any contact with the mouth. Hands should be thoroughly washed after any contact with the specimen. The mineral should be protected from high temperatures and chemicals. ## Storage It is recommended to store specimens in tightly sealed, transparent containers (e.g., micromount boxes), away from areas of constant human presence due to radioactivity. Each container must be clearly and permanently labeled with the mineral name and warnings about toxicity and radioactivity.

Sources

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