Vandenbrandeite

Chemical formula: Cu₂+U₆+O₂(OH)₄

Vandenbrandeite is a rare uranyl copper hydroxide, forming dark green to black, tabular crystals and coatings, prized by collectors of radioactive minerals.

## Characteristics Vandenbrandeite is a rare secondary mineral from the uranyl hydroxide group. It forms characteristic, thin, tabular or bladed crystals of dark green, greenish-black, or even black color. These crystals often occur in clusters, forming radial aggregates, rosettes, or dense coatings and crusts on the host rock. The mineral exhibits strong pleochroism, changing hue from green to bluish-green depending on the observation direction. ## Physical Properties Vandenbrandeite's hardness on the Mohs scale is approximately 4, making it a relatively soft mineral. It has a vitreous luster, approaching subadamantine on some surfaces. It is a dense mineral, with a specific gravity exceeding 5 g/cm³, which is typical for uranium minerals. It is usually translucent, becoming opaque in thicker fragments or compact aggregates. ## Colors and Varieties The dominant and only known color of the mineral is an intense, dark green, which can transition into almost black shades. No color or commercial varieties are distinguished. ## History and Name The mineral was first described in 1932 by the Belgian mineralogist Alfred Schoep. He named it in honor of Pierre Van den Brande, a Belgian geologist working for Union Minière du Haut Katanga, who conducted research in the Democratic Republic of Congo. The type locality (locus typicus) is the Kalongwe deposit in Katanga Province. ## Uses Vandenbrandeite has no industrial applications. Due to its rarity, attractive crystal form, and intense color, it is a valued and sought-after collector's mineral, especially among uranium mineral collectors. It is a highly radioactive mineral.

Properties

Mohs hardness: 4
Luster: Vitreous
Streak: Green
Density: 5.03
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Triclinic

Diagnostic features

## Identification Key diagnostic features of vandenbrandeite are its characteristic dark green to black color, tabular crystal form, and very strong radioactivity. It often forms radial aggregates. Its high density is also helpful in identification. ## Distinguishing from Similar Minerals Vandenbrandeite is sometimes confused with other green secondary uranium minerals. It is distinguished from cuprosklodowskite by its much darker color and tabular, rather than acicular, crystal form. From malachite, with which it can co-occur, it is distinguished by its lack of reaction with hydrochloric acid and strong radioactivity. Unlike torbernite, its crystals are not square and have a different shade of green. ## Crystal Forms Crystals are typically thin, tabular, flattened parallel to the {001} cleavage plane. They often arrange themselves into fan-shaped or radial aggregates and rosettes. It also occurs as dense coatings, crusts, and granular masses that cover the host rock.

Geological environment

## Genesis Vandenbrandeite is a secondary mineral, formed in the oxidation zones of hydrothermal uranium-copper deposits. It forms as a result of the alteration of primary uranium minerals, such as uraninite, under the influence of waters rich in dissolved copper. ## Mineral Associations It most commonly co-occurs with other secondary uranium and copper minerals. Typical associated minerals include cuprosklodowskite, kasolite, uranophane, curite, as well as malachite and heterogenite. ## Localities The most important and well-known vandenbrandeite localities in the world are found in the Katanga Copperbelt in the Democratic Republic of Congo. In addition to the type locality in Kalongwe, beautiful specimens come from the Musonoi and Shinkolobwe mines. Occurrences of this mineral have also been reported in several places in France (e.g., the La Crouzille deposit) and Germany (Saxony).

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized vandenbrandeite specimens are characterized by well-formed, sharp, and lustrous crystals, forming aesthetic, radial aggregates. The intensity and depth of the dark green color are of great importance. The value of a specimen is also enhanced by its placement on a contrasting host rock and its association with other rare uranium minerals. ## Popular Localities Historical finds from mines in the Katanga region of the Democratic Republic of Congo are considered classic and provide the best specimens. Specimens from these localities serve as a benchmark for this mineral and are the most sought after by collectors.

Care and storage

## Cleaning The mineral is very sensitive and requires careful handling. Cleaning should be kept to an absolute minimum. A soft brush or compressed air from a safe distance can be used to remove dust. Washing with water should be strictly avoided, as should cleaning in ultrasonic cleaners, which can damage delicate crystals. ## What to Avoid As a uranium mineral, vandenbrandeite is highly radioactive. Inhaling dust and direct skin contact for prolonged periods should be avoided. Hands should be thoroughly washed after each contact with the specimen. The mineral is relatively soft and has perfect cleavage, making it susceptible to mechanical damage. It should be protected from impacts, scratching, and contact with chemicals, especially acids. ## Storage Vandenbrandeite specimens must be stored in accordance with radiological protection principles. They should be kept in separate, sealed, and clearly labeled containers, away from other minerals that could be damaged by radiation. Storage in a well-ventilated area, away from permanent human presence, is recommended. Serious collectors often use lead-lined containers to block radiation emission.