Metaschoepite

Chemical formula: (U⁶⁺O₂)₈O₂(OH)₁₂·10H₂O

Metaschoepite is a secondary uranium mineral, forming microscopic, yellow to orange-yellow crystals, resulting from the oxidation of uraninite.

## Characteristics Metaschoepite is a hydrated uranyl oxide, found in the oxidation zones of uranium ore deposits. It forms very small, tabular or short-prismatic crystals, which rarely exceed 1 mm in length. It usually occurs as aggregates, coatings, or crusts on uraninite and other uranium minerals. Its crystals are characterized by an intensely yellow, orange-yellow, or yellowish-brown color. ## Physical Properties Metaschoepite crystals exhibit a vitreous to adamantine luster on crystal faces, and on fracture surfaces, it can be dull or earthy. It is a relatively soft mineral, with a Mohs hardness of about 2.5. It is transparent to translucent. Due to its high uranium content, it is a very dense and highly radioactive mineral. ## Colors and Varieties Metaschoepite occurs in shades from sulfur-yellow, through lemon-yellow, orange-yellow, to yellowish-brown. No named varieties are distinguished. ## History and Name The mineral's name refers to its relationship with schoepite. It was originally described as schoepite by V. Billiet in 1936. Clifford Frondel in 1947 showed that schoepite slowly loses water in contact with air, transforming into a more stable phase, which was named metaschoepite. The prefix "meta-" indicates a lower degree of hydration relative to schoepite. ## Applications Metaschoepite, like other secondary uranium minerals, has no direct industrial application. It has scientific significance as an indicator of weathering processes in uranium deposits and is sought after by specialized collectors of radioactive minerals.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
Yellow
Density
0
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Metaschoepite can be identified by its intense yellow color, characteristic form of small, tabular crystals, and co-occurrence with uraninite. A key diagnostic feature is its strong radioactivity, easily detectable with a Geiger counter. Under shortwave ultraviolet radiation, it exhibits strong, yellow-green fluorescence. ## Distinguishing from Similar Minerals It can be confused with other yellow secondary uranium minerals, such as schoepite, becquerelite, fourmarierite, or studtite. Schoepite is less stable and slowly transforms into metaschoepite under ambient conditions. Becquerelite and fourmarierite have a similar appearance but differ subtly in hue and optical properties. Precise identification of these minerals almost always requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Metaschoepite crystals are most often tabular, flattened parallel to the (001) plane, with a hexagonal or octagonal outline. They also occur as short prisms. They typically form radial aggregates, rosettes, as well as coatings and crusts on the host rock.

Geological environment

## Genesis Metaschoepite is a secondary mineral, forming exclusively in the oxidation (weathering) zones of hydrothermal and sedimentary uranium deposits. It forms as a result of slow dehydration of schoepite under atmospheric conditions or through direct oxidation and hydration of uraninite (UO₂). ## Mineral Associations It most commonly co-occurs with uraninite, which is its parent mineral. It is also accompanied by other secondary uranium minerals, such as becquerelite, curite, fourmarierite, rutherfordine, soddyite, kasolite, as well as gypsum, calcite, and clay minerals. ## Localities As a weathering product of uraninite, metaschoepite is found in many uranium deposits worldwide. Key localities include the Shinkolobwe mine in the Democratic Republic of Congo (type locality), Great Bear Lake in Canada, deposits in the Colorado Plateau region (Utah, Arizona, Colorado) in the USA, mines in Jáchymov in the Czech Republic, and Wölsendorf in Bavaria (Germany).

Rarity

Not very common

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp crystals of intense, lemon-yellow or orange color. Attractiveness is enhanced by a clear contrast with dark host rock (most often uraninite). Rich, radial aggregates and rosettes of crystals are also highly valued. Due to the microscopic size of the crystals, specimens with visible, larger crystals (even 1-2 mm) are rare and sought after. ## Popular Localities Classic and most desirable metaschoepite specimens come from the historic locality of Shinkolobwe in the Democratic Republic of Congo. High-quality material was also supplied by mines in Jáchymov (Czech Republic) and some deposits in Utah, USA.

Care and storage

## Cleaning The mineral is very delicate and sensitive to changes in humidity. Mechanical cleaning is not recommended. If necessary, a stream of compressed air can be used to remove dust. Contact with water should be avoided, as it can alter its structure. ## What to Avoid Metaschoepite is a highly radioactive mineral – inhaling dust and direct skin contact must be strictly avoided. It should not be heated, as it easily loses water and undergoes transformations. Store away from heat sources and protect from prolonged exposure to light, which can cause fading. Avoid storing in overly dry or overly humid conditions. ## Storage Metaschoepite specimens must be stored in accordance with safety regulations for radioactive materials. They should be kept in sealed, lead-lined or thick-glass containers, appropriately labeled. Store in a place inaccessible to children and pets, away from frequently used rooms.

External references

Sources

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