Vandermeerscheite

Chemical formula: K<sub>2</sub>[(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>V<sup>5+</sup><sub>2</sub>O<sub>8</sub>]·2H<sub>2</sub>O

Vandermeerscheite is a rare uranyl vanadate mineral, forming microscopic, yellow crystals with intense fluorescence under UV light.

## Characteristics Vandermeerscheite is a hydrated uranyl potassium vanadate. It occurs as very small, tabular or lath-like crystals, rarely exceeding 0.2 mm in length. These crystals are usually flattened and form small aggregates, rosettes, or appear as single flakes on the host rock. Due to its size, magnification is essential for observation. ## Physical Properties Crystals exhibit a vitreous luster and are transparent to translucent. Hardness on the Mohs scale is estimated at around 2, which means it is a very soft mineral. The density calculated from the formula and cell parameters is 4.31 g/cm³. The mineral shows strong, green fluorescence under ultraviolet light (both shortwave and longwave). ## Colors and Varieties This mineral has a characteristic light yellow to golden yellow color. No varieties have been distinguished. ## History and Name The name Vandermeerscheite honors Eddy Vandermeersch (born 1957), a Belgian mineral collector specializing in uranium minerals, who first found this mineral. It was described as a new mineral species in 2017 by Travis A. Olds and co-workers. The type specimen comes from the Musonoi mine in the Democratic Republic of Congo. ## Uses Due to its rarity, microscopic crystal size, and radioactivity, Vandermeerscheite has no industrial applications. It is solely an object of interest for specialized collectors of uranium minerals and scientists.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light yellow
Density
4.31
Cleavage
Perfect on {001}
Fracture
Micaceous
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Key diagnostic features include its light yellow color, tabular habit of very small crystals, and, above all, intense green fluorescence under UV light. Occurrence in association with other secondary uranium minerals in copper-cobalt deposits is also an important clue. ## Distinguishing from Similar Minerals It can be confused with many other yellow secondary uranium minerals, such as carnotite, tyuyamunite, or metatorbernite. Visual differentiation without specialized equipment is practically impossible. Positive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or Raman spectroscopy. ## Crystal Forms It forms very thin, tabular crystals with a rectangular or hexagonal outline. These crystals often group into small, rosette-like or fan-shaped aggregates.

Geological environment

## Genesis Vandermeerscheite is a secondary mineral formed in the oxidation (weathering) zones of uranium-copper-cobalt deposits. It crystallizes from aqueous solutions rich in uranium, vanadium, and potassium, under low temperature and pressure conditions. ## Mineral Associations At the type locality (Musonoi mine), it co-occurs with other rare uranyl vanadate minerals, such as strelkinite, as well as with gypsum, quartz, and tennantite. ## Localities The only confirmed and described occurrence of this mineral in the world is the Musonoi mine, located near the city of Kolwezi, in Lualaba Province, Democratic Republic of Congo.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, the size and quality of crystals are most important, although even the best specimens are microminerals. Rich clusters of well-formed, sharp crystals with an intense yellow color, contrasting with the darker host rock, are prized. The presence of associated minerals can increase the specimen's value. ## Popular Localities The only source of specimens of this mineral is its type locality – the Musonoi mine in the Democratic Republic of Congo. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Vandermeerscheite specimens should generally not be wet cleaned. Dust can be removed very carefully with a soft brush or a photographic air blower. Any contact with water or other liquids can damage the delicate crystals. ## What to Avoid Contact with water and chemicals must be strictly avoided. The mineral is very soft and brittle, so it should be protected from impacts and abrasions. As a uranium mineral, it is radioactive – exposure should be limited, and dust inhalation avoided. Always wash hands after handling the specimen. ## Storage Specimens should be stored in sealed, clearly labeled containers (e.g., "perky boxes"), away from other minerals that could be damaged by radiation. Store in a dry place, away from heat sources and direct sunlight, out of reach of children and pets.

Sources

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