Vandendriesscheite

Chemical formula: Pb²⁺₁.₆(U⁶⁺O₂)₁₀O₆(OH)₁₁·₁₁H₂O

Vandendriesscheite is a rare, secondary uranium mineral, forming characteristic orange-red to yellow, tabular crystals.

## Characteristics Vandendriesscheite is a hydrated lead uranium oxide, occurring in the oxidation zones of uraninite deposits. It forms aggregates of small, tabular or short-prismatic crystals, often arranged in rosette-like or fan-shaped aggregates. Specimens typically have an intense orange-red, orange-yellow, or golden-orange color, which makes them visually distinctive. ## Physical Properties This mineral is relatively soft, with a hardness of about 3 on the Mohs scale. Crystals exhibit a vitreous to adamantine luster on faces and a slightly pearly luster on cleavage planes. It is transparent to translucent. Due to its uranium and lead content, it has a high density, approximately 5.05 g/cm³. ## Colors and Varieties The dominant colors range from orange-yellow, through golden-orange, to orange-red. No named varieties of this mineral are distinguished. ## History and Name The mineral is named in honor of Adrien Vandendriessche (1875-1940), a Belgian geologist and professor at Ghent University. The mineral was first described in 1947 by Johannes Vaes based on samples from the Shinkolobwe mine in the Democratic Republic of Congo. ## Uses Vandendriesscheite, due to its rarity and small accumulations, has no industrial applications. However, it is a valued and sought-after collector's mineral because of its intense color, attractive crystal forms, and association with other rare uranium minerals. As a highly radioactive mineral, it is also an object of scientific research.

Properties

Mohs hardness: 3
Color: Orange to amber-brown
Luster: Adamantine, Vitreous, Pearly
Streak: Pale yellow
Density: 5.45
Cleavage: {001}
Fracture: Uneven
Transparency: Transparent,Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Key diagnostic features include an intense orange-red or yellow color, characteristic tabular crystals often forming fan-shaped aggregates, and high density. The most important feature is strong radioactivity, easily detectable with a Geiger counter. The mineral also exhibits yellow-green fluorescence under ultraviolet (UV) light. ## Distinguishing from Similar Minerals It can be confused with other secondary uranium minerals of similar color, such as curite, fourmarierite, or becquerelite. Curite is usually redder and forms acicular crystals. Fourmarierite has a similar habit but often a darker, reddish-brown hue. Becquerelite is more yellow. Definitive differentiation often requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Crystals are most often tabular, flattened along one of the crystallographic axes, or short-prismatic. They frequently occur as radial, fan-shaped, or rosette-like aggregates, as well as coatings and crusts on uraninite.

Geological environment

## Genesis Vandendriesscheite is a secondary mineral, formed by the weathering (oxidation) of primary uranium ores, mainly uraninite, in the presence of lead-rich solutions. It forms near the Earth's surface, in the oxidation zone of hydrothermal deposits. ## Mineral Associations It most commonly co-occurs with uraninite (as the primary mineral) and other secondary uranium minerals, such as becquerelite, curite, fourmarierite, masuyite, rutherfordine, schoepite, kasolite, and torbernite. ## Localities The most important and classic locality, from which the best specimens originate, is the Shinkolobwe mine in Katanga Province, Democratic Republic of Congo. It is also known from several other localities worldwide, including the Kasolo mine (also in Katanga), Rabéjac in France, and some pegmatites in Norway.

Rarity

Rare

For collectors

## Quality Criteria The most highly prized vandendriesscheite specimens are characterized by sharply terminated, well-formed crystals with an intense, orange-red color. Aesthetic, fan-shaped or rosette-like aggregates set on a contrasting rock matrix enhance their attractiveness. Crystal size and the absence of mechanical damage are also important. ## Popular Localities Specimens from the type locality – the Shinkolobwe mine in the Democratic Republic of Congo – are by far the most sought after by collectors. They are considered the global standard for this mineral.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft brush or compressed air to remove dust. The use of water is not recommended, as it may affect the mineral's stability. Ultrasonic cleaners should be avoided. ## What to Avoid The mineral is highly radioactive – it is absolutely essential to avoid inhaling dust and direct skin contact. It requires careful handling and hand washing after each contact. It should not be heated or exposed to chemicals. Prolonged exposure to sunlight may cause fading. ## Storage Due to its radioactivity, vandendriesscheite specimens must be stored in special, sealed, and appropriately labeled containers, away from areas of permanent human habitation. It is best to keep them in lead-lined boxes, which block radiation. It should be isolated from other radiation-sensitive minerals.

External references

https://www.mindat.org/min-4145.html