Bijvoetite-(Y)

Chemical formula: Y<sub>8</sub>(U<sup>6+</sup>O<sub>2</sub>)<sub>16</sub>O<sub>8</sub>(CO<sub>3</sub>)<sub>16</sub>(OH)<sub>8</sub>·39H<sub>2</sub>O

Bijvoetite-(Y) is a very rare, highly radioactive uranyl mineral, forming microscopic, yellow crystals and coatings.

## Characteristics Bijvoetite-(Y) is a hydrated yttrium uranyl carbonate. It occurs as very small, thin, tabular crystals, usually not exceeding 0.1 mm, which often form rosette-like aggregates, spherulitic clusters, or thin coatings and efflorescences on other minerals. Due to the microscopic size of the crystals, its visual features are difficult to observe without magnification. ## Physical Properties The crystals exhibit a luster described as vitreous to pearly, especially on cleavage surfaces. The mineral is transparent to translucent. It is very soft, with a Mohs hardness of 2. Due to its uranium content, it is highly radioactive. ## Colors and Varieties Bijvoetite-(Y) has a characteristic light yellow to yellowish-green color. The streak is pale yellow. No color or commercial varieties are distinguished. ## History and Name The mineral was described in 1982 by Michel Deliens and Paul Piret. It was named in honor of Johannes Martin Bijvoet (1892–1980), a Dutch crystallographer and chemist who developed a method for determining the absolute configuration of molecules. The suffix "-(Y)" refers to the dominant rare earth element – yttrium. The type locality is the Shinkolobwe mine in the Democratic Republic of Congo. ## Uses Bijvoetite-(Y) has no industrial applications. It is of purely scientific interest and is an object of interest for specialized collectors of rare uranium minerals.

Properties

Mohs hardness
2
Luster
Vitreous to Pearly
Streak
Pale yellow
Density
3.9
Cleavage
Perfect on {001}
Fracture
Micaceous
Transparency
Transparent to Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identifying bijvoetite-(Y) in practice requires advanced laboratory methods, such as X-ray diffraction (XRD). Preliminary identification in a collection is based on its characteristic light yellow color, the specific form of microscopic, tabular crystals forming rosettes, and its co-occurrence with other secondary uranium minerals. Strong radioactivity is a key diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with many other yellow secondary uranium minerals, such as schoepite, studtite, or rutherfordine. Visual differentiation is practically impossible and requires chemical or crystallographic analysis. Mineral associations and crystal habit can be helpful clues. ## Crystal Forms It forms very thin, tabular crystals with a hexagonal or octagonal outline. These crystals almost always occur as radial or rosette-like aggregates and spherulites. Less commonly, it forms coatings and efflorescences.

Geological environment

## Genesis Bijvoetite-(Y) is a secondary mineral formed in the oxidation zones of uraninite deposits. It forms as a result of the weathering of primary uranium ores in the presence of carbonate-rich and yttrium-rich waters. ## Mineral Associations It most commonly co-occurs with uraninite (as a primary mineral) and other secondary uranium minerals, such as becquerelite, curite, rutherfordine, schoepite, kasolite, and sklodowskite. ## Localities This is an extremely rare mineral. Apart from its type locality – the Shinkolobwe mine in the Democratic Republic of Congo – its occurrence has been confirmed in only a few other places worldwide, including the Rössing uranium mine in Namibia and the Lake Athabasca region in Saskatchewan, Canada.

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of a specimen depends on the abundance and development of microcrystals. The most prized specimens are those with clearly formed, lustrous, rosette-like aggregates of bijvoetite-(Y) on a contrasting matrix, for example, on dark uraninite. The aesthetics of the entire associated mineral assemblage are also important. ## Popular Localities By far the most known and valued specimens, serving as the type material for this mineral, come from its type locality – the Shinkolobwe mine in the Democratic Republic of Congo.

Care and storage

## Cleaning Bijvoetite-(Y) specimens are generally not cleaned due to their extreme delicacy and microscopic size. Any attempt at mechanical cleaning, even with a soft brush, risks destroying the fragile crystals. Dust can be removed very carefully using a photographic air blower. ## What to Avoid Contact with water and chemicals, which can dissolve or damage the mineral, must be strictly avoided. As a secondary mineral, it is unstable and sensitive to changes in humidity and temperature. Due to its strong radioactivity, exposure should be limited, and hands should always be washed after contact with the specimen. ## Storage Specimens should be stored in airtight, sealable containers (such as "perky boxes") to protect them from mechanical damage and humidity changes. Containers should be clearly labeled as radioactive material and stored away from other minerals that could be damaged by radiation.

External references

Sources

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