Alexshubnikovite

Chemical formula: Ca₂Cu₂+₉(As₅+O₄)₄(OH)₉Cl(H₂O)₈·₂H₂O

A very rare hydrated calcium copper arsenate containing chlorine, discovered in the oxidation zone of a nickel-cobalt deposit in Tuva.

## Characteristics Alexshubnikovite is a chemically complex mineral belonging to the arsenate class. Its structure contains calcium ions, copper, hydroxyl groups, chlorine, and water molecules. As a copper mineral, it forms microscopic crystals and aggregates typical of secondary ore oxidation zones. ## Physical properties Due to its recent discovery and extreme rarity, specimens of this mineral are typically microscopic in nature, making the macroscopic determination of many physical properties difficult. ## Colors and varieties It has no known varieties. ## History and name The mineral was approved by the International Mineralogical Association (IMA) in 2022. Its name honors Alexey Vasilyevich Shubnikov (1887-1970), a prominent Russian crystallographer and physicist, founder of the Institute of Crystallography of the Russian Academy of Sciences. The type locality is the Khovu-Aksy deposit in Tuva. ## Uses Due to its extreme rarity, this mineral is of purely scientific and systematic significance.

Properties

Crystal system: Monoclinic

Diagnostic features

## Identification Macroscopic identification of alexshubnikovite is practically impossible without advanced analytical methods, such as X-ray diffraction (XRD) or spectroscopy. It occurs in the form of microscopic crystals. ## Distinguishing from similar minerals It must be distinguished from other secondary copper and calcium arsenates co-occurring in the oxidation zones of arsenide deposits. Definitive identification relies on structural and chemical analyses. ## Crystal forms It crystallizes in the monoclinic system. It forms microcrystals and fine aggregates in rock cavities.

Geological environment

## Origin It is a secondary mineral formed in the oxidation zones of arsenic-rich hydrothermal nickel and cobalt ore deposits. It crystallizes from aqueous solutions at low temperatures as a result of the weathering of primary arsenides. ## Mineral associations It co-occurs with other secondary minerals of the oxidation zone, including copper, cobalt, and nickel arsenates. ## Localities The only confirmed locality (locus typicus) is the Khovu-Aksy nickel-cobalt deposit in the Chedi-Kholsky District, Tuva, Russia.

Rarity

Extremely rare

For collectors

## Quality criteria Collector value is based solely on rarity and confirmed systematics. Specimens are in micromount format, and their appeal is determined by the richness of the mineral association and the clarity of the crystals under a microscope. ## Popular localities The Khovu-Aksy deposit in Russia is the sole source of specimens of this mineral.

Care and storage

## Cleaning Requires great care. Specimens should be cleaned using compressed air only. Washing in water should be avoided due to the presence of water molecules in the structure and potential sensitivity to dissolution. ## What to avoid Contact with acids, detergents, and environments with extreme humidity, which could lead to dehydration or structural degradation, must be strictly avoided. Protect from elevated temperatures. ## Storage Store in airtight containers (micromount boxes) that protect against dust, mechanical damage, and sudden changes in atmospheric conditions.

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External references

https://www.mindat.org/min-499624.html