Borzęckiite

Chemical formula: Pb<sup>2+</sup>(U<sup>6+</sup>O<sub>2</sub>)<sub>3</sub>(Se<sup>4+</sup>O<sub>3</sub>)<sub>2</sub>O<sub>2</sub>·3H<sub>2</sub>O

Borzęckiite is an extremely rare, secondary uranyl and lead mineral, forming microscopic, yellow, tabular crystals.

## Characteristics Borzęckiite is a hydrated uranyl and lead selenite. It occurs as extremely small, tabular or bladed crystals, reaching up to 0.2 mm in size, which form radial or irregular aggregates and clusters. The crystals are elongated and flattened, often with striations on their surfaces. ## Physical Properties Borzęckiite crystals exhibit a yellow luster, described as vitreous to slightly resinous. Due to the microscopic size of the crystals, most physical properties, such as hardness or density, have not been precisely measured. The density was calculated based on the formula and unit cell parameters and is approximately 6.05 g/cm³. ## Colors and Varieties This mineral has a characteristic, light yellow color. The streak is light yellow. No varieties have been distinguished. ## History and Name Borzęckiite was discovered in the inactive uranium mine "Miedzianka" in the Świętokrzyskie Mountains, Poland. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2021. The name honors the Polish mineral collector, Piotr Borzęcki (born 1963), who found the first samples of this mineral. ## Uses Borzęckiite, due to its extreme rarity and microscopic size, has no industrial application. It is solely an object of scientific and collecting interest for specialized collectors of micromount minerals.

Properties

Luster
Vitreous to Resinous
Streak
Light yellow
Density
6.05
Cleavage
Perfect on {001}
Transparency
Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of borzęckiite is possible almost exclusively under laboratory conditions using advanced techniques such as Raman spectroscopy or X-ray diffraction (XRD). Visually, in the field or in a collection, identification is practically impossible. A characteristic feature under the microscope is very small, yellow, tabular crystals forming radial aggregates. ## Distinguishing from similar minerals Borzęckiite can be confused with other yellow secondary uranium minerals, such as marthozite, guilleminite, or demesmaekerite, with which it co-occurs. Certain differentiation requires chemical and structural analysis, as these minerals have a very similar appearance and often form intergrowths. ## Crystal forms Borzęckiite crystals are tabular, flattened, and elongated, often with visible striations. They form small, radial or chaotic clusters on the host rock.

Geological environment

## Genesis Borzęckiite is a secondary mineral that forms in the oxidation (weathering) zone of uranium-copper deposits. It is formed by the interaction of selenium-bearing waters with earlier uranium and lead minerals, such as uraninite and galena, in the presence of oxygen. ## Mineral associations This mineral occurs in association with other secondary uranyl selenites. It most commonly co-occurs with marthozite, guilleminite, demesmaekerite, as well as gypsum, malachite, chrysocolla, quartz, and hematite. ## Localities The only confirmed occurrence of borzęckiite in the world is its type locality – the dumps of the former uranium mine "Miedzianka" near Chęciny, in the Świętokrzyskie Mountains, Poland.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of borzęckiite specimens is assessed primarily based on the abundance and visibility of crystals in the aggregate. The most prized samples are those where clear, well-formed, radial clusters of yellow crystals, contrasting with the darker host rock, can be seen with the naked eye or under slight magnification. The size of individual crystals, although always microscopic, also affects the value. ## Popular localities The only source of specimens is the "Miedzianka" mine in Poland. Specimens from this locality are by definition the most desirable, as it is the only known place of their occurrence.

Care and storage

## Cleaning Specimens should not be wet cleaned. Dust can only be removed using compressed air or a very soft brush, with utmost care due to the fragility and small size of the crystals. ## What to avoid Contact with water, chemicals, ultrasound, and sudden temperature changes must be strictly avoided. The mineral is radioactive and should be handled according to safety regulations for radioactive materials – avoid inhaling dust and wash hands after each contact. ## Storage Specimens should be stored in tightly sealed, transparent "micromount" containers, protecting them from dust, moisture, and mechanical damage. Store away from other minerals that could be damaged by radiation.

Sources

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