Součekite

Chemical formula: Cu₁+Pb₂+Bi₃+(S₂-,Se₂-)₃

Součekite is a rare copper, lead, and bismuth sulfoselenide, forming metallic, steel-gray to black aggregates.

## Characteristics Součekite is a mineral from the bournonite group, a complex copper, lead, and bismuth sulfoselenide. It typically occurs as anhedral (irregularly formed) grains or massive aggregates, rarely forming small, lamellar crystals. It has a metallic luster and a steel-gray to black color. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness is 3.5-4, making it relatively soft. The density is high, reaching approximately 7.37 g/cm³. ## Colors and Varieties Součekite is monochromatic – its color ranges from steel-gray to black. No distinct color varieties or commercial varieties are recognized. The sulfur to selenium ratio in its chemical composition can be variable, but this does not significantly affect its external appearance. ## History and Name The mineral was first described in 1979 by V. Hoffman, Z. Trdlička, S. V. Kholodov, and T. N. Krylova. The name "součekite" was given in honor of František Souček (1911-1977), a Czech mineral collector and curator of the National Museum in Prague, who first found this mineral. ## Uses Due to its rarity, součekite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and scientists.

Properties

Mohs hardness: 3.5-4
Luster: Metallic
Streak: Black
Density: 7.37
Cleavage: Poor on {010}
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of součekite is based on its physical properties: steel-gray color, metallic luster, black streak, and high density. It occurs in a characteristic geological environment. ## Distinguishing from Similar Minerals It can be confused with other sulfosalts and selenides of similar appearance, such as bournonite, aikinite, or clausthalite. Definitive differentiation requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD), due to the similarity of physical properties. ## Crystal Forms It most often forms massive, granular aggregates or irregular grains intergrown with other minerals. Small, lamellar or tabular crystals up to several millimeters long are rarely observed.

Geological environment

## Genesis Součekite forms under hydrothermal conditions, in polymetallic ore veins containing selenium. ## Mineral Associations It co-occurs with other selenides and sulfides, such as berzelianite, umangite, eskebornite, clausthalite, tiemannite, as well as with uraninite, chalcopyrite, pyrite, and hematite. ## Localities The most important and type locality is Oldřichov near Tachov in the Czech Republic. It is also known from the Zálesí uranium deposit in the Czech Republic and from the Tumiñico mine in La Rioja province, Argentina.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, specimens rich in součekite are most valuable, preferably in the form of visible, even if small, crystals or distinct aggregates on a rock matrix. Analytically confirmed mineral identity is crucial. ## Popular Localities The most prized specimens come from the type locality – Oldřichov in the Czech Republic.

Care and storage

## Cleaning Specimens should only be dry-cleaned, using a soft brush to remove dust. Avoid water and any chemical agents. ## What to Avoid As a sulfoselenide, součekite can be sensitive to moisture and oxidation in the long term. It should be protected from contact with chemicals, acids, and humid air. Due to its low hardness, it is susceptible to scratching. ## Storage It is recommended to store specimens in dry, stable conditions, preferably in closed display boxes or cabinets away from dust and moisture.

Sources

IMA Mineral List (CNMNC)