Chromviskontite

Chemical formula: Pb₂+₅Cu₂+₂(Cr₆+O₄)₃(Se₄+O₃)(OH)₆

Chromviskontite is a rare mineral from the chromate group, distinguished by its intense orange color and occurrence as fine, acicular crystals.

## Characteristics Chromviskontite is a complex lead and copper chromate with selenium additions. It forms very small, acicular or bladed crystals, rarely exceeding 0.2 mm in length. They typically occur as radial or tangled aggregates, as well as single needles scattered on the surface of the host rock. Its most characteristic feature is its vivid orange color. ## Physical Properties The crystals are too small to precisely determine their hardness; however, based on their chemical composition, it can be assumed to be a relatively soft mineral. The luster is described as vitreous to adamantine. Due to the small size of the crystals, accurate density measurements have not been performed. ## Colors and Varieties This mineral occurs in a uniform, intensely orange color. No color varieties or commercial varieties are known. ## History and Name Chromviskontite was first described in 2023 by a team of mineralogists (I. V. Pekov et al.). Its name refers to its chemical composition – the dominant chromium (Cr) – and to its structural and chemical similarity to the mineral viskontite. The name was approved by the International Mineralogical Association (IMA2023-010). ## Uses Due to its extreme rarity and microscopic size, chromviskontite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized rare mineral collectors.

Properties

Luster: Vitreous to Adamantine
Streak: Orange
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of chromviskontite is based on its characteristic, intense orange color, acicular crystal habit forming radial aggregates, and its unique occurrence environment. Definitive identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS), due to its coexistence with other visually similar, rare minerals. ## Distinguishing from Similar Minerals Chromviskontite can be confused with other orange chromates from the same locality, such as crocoite or embreyite. Distinguishing it from these minerals with the naked eye is practically impossible and requires specialized studies. However, the form of acicular, radial aggregates is quite characteristic. ## Crystal Forms This mineral forms very fine, acicular or bladed crystals, usually grouped into radial or chaotic aggregates. Single crystals are rare.

Geological environment

## Genesis Chromviskontite is a secondary mineral, forming in the oxidation zones (gossans) of polymetallic deposits. Its formation is associated with the weathering processes of primary ore minerals in the presence of solutions rich in chromium, lead, copper, and selenium. ## Mineral Associations This mineral occurs in association with other rare secondary minerals. It most commonly coexists with anglesite, cerussite, chalcophanite, choloalite, crocoite, embreyite, phoenicochroite, fornacite, mimetite, pyromorphite, wulfenite, and iron and manganese oxides (e.g., goethite). ## Localities The only confirmed locality for chromviskontite in the world is the Berezovskoye mine (Berezovsk) in the Sverdlovsk Oblast, Ural Mountains, Russia. This is the type locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly prized chromviskontite specimens are those that possess rich, well-formed, and undamaged aggregates of acicular crystals, clearly standing out against the host rock. Due to the microscopic size of the crystals, the aesthetics of the entire aggregate and its photogenicity under magnification are crucial. Contrast with associated minerals, such as white cerussite, also enhances the specimen's value. ## Popular Localities The only source of specimens is the Berezovskoye mine in Russia, which is world-renowned for providing exceptional specimens of crocoite and other rare chromates.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Due to the extreme delicacy of the microscopic crystals, any mechanical contact, including with a soft brush, is highly risky and can lead to the destruction of the aggregates. ## What to Avoid Contact with water, acids, bases, and all chemical agents must be strictly avoided. The mineral is likely sensitive to changes in temperature and humidity. It should not be exposed to direct sunlight, which may cause it to fade. ## Storage Chromviskontite specimens should be stored under stable conditions, preferably in tightly sealed "micromount" boxes, which protect them from dust, mechanical damage, and humidity fluctuations.

Sources

IMA Mineral List (CNMNC)