Petrovicite

Chemical formula: Cu₁+₃Hg₂+Pb₂+Bi₃+Se₂-₅

Petrovicite is a rare copper, mercury, lead, and bismuth selenide, forming metallic, fibrous aggregates.

## Characteristics Petrovicite is a very rare mineral from the sulfide group, specifically a selenide. It occurs as fibrous or acicular aggregates, which can form masses resembling felted wool or mats. Individual crystals are too small to be seen with the naked eye. It has a metallic luster and a steel-gray to black color. ## Physical Properties This mineral is characterized by a metallic luster and a black streak. It is opaque. Due to its occurrence in the form of fine, felted aggregates, determining its hardness and density is difficult; the density calculated based on the chemical formula and unit cell parameters is 8.45 g/cm³. ## History and Name Petrovicite was first described in 1976 by J. Hak, Z. Johan, M. Kvaček, and W.G. Liebscher. Its name honors two individuals: Radomir Petrović, a Czech mineral collector who found the first samples, and Professor Ivica Petrović from the University of Zagreb, a researcher of bauxite deposits. The type locality (locus typicus) is the Předbořice uranium deposit in the Czech Republic. ## Applications Petrovicite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and scientists studying the mineralogy of ore deposits.

Properties

Luster: Metallic
Streak: Black
Density: 8.45
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Petrovicite is identified by its unique form – tangled, fibrous or acicular aggregates of a steel-gray color and metallic luster. Key to identification is its occurrence in a specific geological environment, in association with other selenides. ## Distinguishing from Similar Minerals It can be confused with other fibrous sulfides or selenides, such as jamesonite, boulangerite, or clausthalite. Final differentiation requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS), due to its characteristic chemical composition including copper, mercury, lead, bismuth, and selenium. ## Crystal Forms It forms acicular or hair-like crystals up to 1 mm long, which usually occur as dense, tangled aggregates.

Geological environment

## Genesis Petrovicite is a hydrothermal mineral. It forms in low-temperature calcite veins cutting uranium-polymetallic deposits. Its crystallization is associated with selenide mineralization processes. ## Mineral Associations It most commonly co-occurs with calcite, clausthalite, berzelianite, umangite, eskebornite, uraninite, hematite, and goethite. This specific association is an important diagnostic clue. ## Localities The most important and type locality is the historical Předbořice uranium mine, near the town of Kovářov in southern Bohemia, Czech Republic. This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Extremely rare

For collectors

## Quality Criteria The most prized petrovicite specimens are those with rich, dense, and well-preserved fibrous aggregates on a contrasting matrix, most often white calcite. The size and abundance of petrovicite clusters are key factors influencing the value of a specimen. Due to its extreme rarity, any authentic specimen is considered valuable. ## Popular Localities The only source of collector specimens is the type locality – Předbořice in the Czech Republic. Material from this locality is extremely difficult to obtain, as the mine has long been inactive and reclaimed.

Care and storage

## Cleaning Petrovicite specimens should generally not be cleaned. Fibrous aggregates are extremely delicate and brittle. Any attempt at mechanical cleaning, even with a soft brush, risks irreversible damage to the specimen. Contact with water and any chemicals should be avoided. ## What to Avoid Avoid vibrations, shocks, and touching. The mineral is very susceptible to mechanical damage. Due to its mercury and lead content, direct skin contact should be avoided, and hands should be washed after any contact. ## Storage Petrovicite specimens require storage in stable conditions, preferably in a sealed, padded "micromount" box, which protects them from dust, shocks, and direct contact. It should not be exposed to moisture or extreme temperatures.

Sources

IMA Mineral List (CNMNC)