Vanuralite

Chemical formula: Al(U⁶⁺O₂)₂(V⁵⁺O₄)₂(OH)·₈.₅H₂O

Vanuralite is a rare, bright yellow uranyl and vanadium mineral, forming tiny, platy crystals and crusts.

## Characteristics Vanuralite is a hydrated uranyl vanadate of aluminum. It most commonly occurs as tiny, platy or bladed crystals, which form rosette-like aggregates, fan-shaped clusters, and earthy or powdery crusts on host rocks. Its characteristic feature is an intense, lemon-yellow to canary-yellow color. Due to its uranium content, it is a radioactive mineral. ## Physical Properties Vanuralite crystals are very small and brittle. This mineral exhibits strong fluorescence under ultraviolet light, glowing green. It is relatively soft, and its density is higher than average for non-ore minerals, which is due to the presence of heavy uranium in its structure. ## Colors and Varieties Vanuralite occurs in a uniform, characteristic range of colors from lemon-yellow to canary-yellow. No named color varieties or commercial names are distinguished for it. ## History and Name The mineral's name refers to its chemical composition – the presence of vanadium (Van), uranium (Ur), and aluminum (Al). It was first described in 1963 based on material collected from the Mounana mine in Gabon. ## Uses Vanuralite, like other secondary uranium minerals, has no direct industrial application due to its rarity and occurrence in small quantities. It is an object of scientific interest and is valued by specialized collectors of uranium minerals.

Properties

Mohs hardness: 2
Color: Citron-yellow, canary-yellow, pale yellow
Luster: Vitreous
Streak: Light yellow
Density: 3.62
Cleavage: On {001}
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Vanuralite can be identified by its characteristic, bright, lemon-yellow color, typical forms of occurrence as tiny, platy crystals forming rosettes and crusts, and strong green fluorescence under UV light. A key diagnostic feature is its radioactivity, detectable with a Geiger counter. ## Distinguishing from Similar Minerals Vanuralite is sometimes confused with other yellow secondary uranium minerals, such as carnotite, tyuyamunite, or francevillite. Carnotite and tyuyamunite often form more earthy and powdery coatings. Francevillite, with which it often co-occurs, has a similar habit but crystallizes in the orthorhombic system and has a slightly different hue. Final distinction requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Crystals are very small, with a platy or bladed habit, often flattened parallel to the {010} plane. They typically form fan-shaped or rosette-like aggregates, as well as thin coatings and crusts on rock surfaces.

Geological environment

## Genesis Vanuralite is a secondary mineral, forming in the oxidation (weathering) zones of uranium and vanadium deposits, especially those deposited in sedimentary rocks, such as sandstones. It forms as a result of groundwater acting on primary uranium minerals (e.g., uraninite) and vanadium in the presence of aluminum. ## Mineral Associations This mineral often co-occurs with other secondary uranium and vanadium minerals. The most common associations include francevillite, curienite, chervetite, as well as uraninite, barite, goethite, and various clay minerals. ## Localities The most important and classic locality for vanuralite is the Mounana mine in the Haut-Ogooué Province of Gabon, from which the best specimens originate. It is also known from several other localities worldwide, including the uranium mines in the Lodève region of France and small occurrences in Spain.

Rarity

Rare

For collectors

## Quality Criteria Specimens with well-formed, distinct crystals forming aesthetic, rosette-like or fan-shaped aggregates are most valued by collectors. The intensity and purity of the lemon-yellow color also increase the specimen's value. The contrast with the rock matrix and the presence of associated minerals, especially rare francevillite or curienite, are also important. ## Popular Localities By far the most sought-after and highly valued vanuralite specimens come from its type locality – the Mounana mine in Gabon. Material from this location is considered the global standard for this mineral.

Care and storage

## Cleaning Vanuralite specimens should generally not be wet cleaned. Small, brittle crystals can suffer mechanical damage. Dust can be removed very carefully with a soft brush or a photographic air blower. Due to radioactivity, all operations should be performed with caution, avoiding inhalation of dust. ## What to Avoid Avoid contact with water, which can damage delicate crystals. The mineral is sensitive to acids and other chemicals. It should not be heated or exposed to prolonged strong sunlight. Wash hands after each contact with the specimen. ## Storage Vanuralite must be stored with consideration for its radioactivity. It is recommended to keep it in a tightly sealed, labeled container (e.g., a plastic "perky box"), away from areas of permanent human habitation, especially bedrooms. It should be stored separately from other minerals that could be damaged by radiation.