Vochtenite

Chemical formula: Fe²⁺Fe³⁺(U⁶⁺O₂)₄(PO₄)₄(OH)·12-13H₂O

Vochtenite is a rare, hydrated iron uranyl phosphate, forming characteristic, tabular, brown crystals.

## Characteristics Vochtenite is a complex, hydrated phosphate containing iron in the divalent and trivalent oxidation states, and a uranyl group. This mineral forms very small, usually not exceeding 1 mm, tabular or bladed crystals. They most often occur as radial or chaotic aggregates and clusters. Its characteristic feature is a brown, often brownish-brown, color. ## Physical Properties Vochtenite crystals are relatively soft, with a Mohs hardness of 2.5. They are translucent to opaque. The mineral's density is approximately 3.65 g/cm³. It exhibits distinct cleavage in one direction. ## Colors and Varieties This mineral occurs in a uniform, brown color, which can be described as brownish-brown. No color varieties or commercial varieties have been distinguished. ## History and Name The mineral's name honors the Belgian mineralogist and professor at the University of Antwerp, Renaud Vochten (1933-2012), for his contributions to the study of uranyl minerals. The mineral was described and approved as a new species in 1993. ## Uses Due to its extreme rarity, small crystal size, and uranium content, vochtenite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals or uranium minerals.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
Pale brown
Density
3.650
Cleavage
Prominent on (010).
Fracture
Irregular/Uneven
Transparency
Translucent,Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of vochtenite include its brown color, tabular crystal habit forming radial aggregates, and occurrence in the oxidation zones of uranium deposits. A pale, brown streak is also helpful in identification. However, final confirmation requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other secondary brown uranium minerals, such as schoepite or paraschoepite, but differs from them in crystal habit and chemical composition (presence of iron and phosphorus). Distinguishing it from other rare uranyl phosphates is impossible without specialized studies. ## Crystal Forms Crystals are tabular, flattened parallel to (010), and often elongated. They form rosette-like, radial, or randomly oriented clusters and aggregates on the surface of the host rock.

Geological environment

## Genesis It is a secondary mineral, forming in the oxidation (weathering) zones of uranium deposits. It forms as a result of the alteration of primary uranium minerals, such as uraninite, in the presence of solutions rich in phosphates and iron. ## Mineral Associations It most often co-occurs with other secondary uranium minerals. At the type locality (Wheal Basset mine in Cornwall), it was found in association with uraninite, chalcopyrite, fluorite, quartz, metatorbernite, and bassetite. ## Localities This is an extremely rare mineral. Apart from the type locality at the Wheal Basset mine in Cornwall (United Kingdom), its occurrence has been reported in only a few other places worldwide, including the Uranus mine near Kleinrückerswalde in Saxony (Germany).

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens are those with clearly formed, undamaged crystals creating aesthetic, radial aggregates on a contrasting rock matrix. Due to the microscopic size of the crystals, the size of the aggregate and the richness of its occurrence on the specimen are key factors influencing its value. The purity and intensity of the color also play a role. ## Popular Localities The only source of collector-grade specimens is the historical type locality – the Wheal Basset mine in Cornwall, United Kingdom. Specimens from this location are extremely sought after and difficult to acquire.

Care and storage

## Cleaning Vochtenite specimens are extremely delicate and fragile. Cleaning should be kept to an absolute minimum. If necessary, a very soft brush can be used to remove loose dust particles. Avoid contact with water and any chemical agents. ## What to Avoid As a uranyl mineral, vochtenite is radioactive and requires careful handling. Direct, prolonged skin contact should be avoided, and dust inhalation must be absolutely prevented. It should not be heated or exposed to acids. Due to its fragility, all vibrations and impacts should be avoided. ## Storage Specimens should be stored in tightly sealed, clearly labeled containers (e.g., "perky box" type), 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.

External references

Sources

Read more