Staročeskéite

Chemical formula: Ag₁+₀.₇₀Pb₂+₁.₆₀(Bi₃+₁.₃₅Sb₃+₁.₃₅)S₂-₆

Staročeskéite is a rare lead-silver sulfosalt of bismuth and antimony, forming tiny, metallic inclusions in quartz veins.

## Characteristics Staročeskéite is a mineral from the sulfosalt group, occurring as very fine, acicular or lamellar crystals, which rarely exceed 1 mm in length. It typically forms inclusions within a quartz matrix or is found in association with other sulfosalts. Its crystals are opaque and have a metallic luster, with colors ranging from steel-gray to tin-white. ## Physical Properties This mineral is characterized by a metallic luster. Due to the microscopic size of its crystals, many of its physical properties, such as hardness or density, have not been precisely measured, but rather calculated based on its chemical formula and unit cell parameters. The calculated density is approximately 6.55 g/cm³. ## Colors and Varieties Staročeskéite is a mineral with a constant composition and does not form color varieties. Its color is uniform, steel-gray to tin-white. In reflected light under a microscope, it exhibits weak pleochroism from white to cream. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2016. Its name comes from the historical region of Old Bohemia (Staré Čechy), where the Kutná Hora mine, the site of its discovery, is located. It was described by a team of mineralogists led by Jiří Sejkora. ## Applications Staročeskéite has no industrial or commercial applications. Its significance is purely scientific and collectible, as a rare and newly discovered mineral species.

Properties

Luster: Metallic
Streak: Black
Density: 6.55
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of staročeskéite is impossible with the naked eye and requires advanced laboratory techniques. Recognition is based on chemical analysis (electron microprobe) to determine the proportions of Ag, Pb, Bi, Sb, and S, and on X-ray diffraction (XRD) to confirm the crystal structure. In the field or in a collection, it can only be suspected based on its co-occurrence with other sulfosalts in quartz veins at known localities. ## Distinguishing from Similar Minerals Staročeskéite is visually indistinguishable from many other sulfosalts with similar silvery or gray color and metallic luster, such as lillianite, gustavite, or pavonite. Definitive differentiation is possible only through analytical methods. ## Crystal Forms It forms elongated, acicular or lamellar crystals, often with visible striations on the faces. These crystals typically occur as single inclusions or form small, radial aggregates within quartz.

Geological environment

## Genesis Staročeskéite is a hydrothermal mineral. It forms in the final stages of crystallization in ore veins, at relatively low temperatures. Its presence is associated with polymetallic mineralization rich in silver, lead, bismuth, and antimony. ## Mineral Associations This mineral occurs in close association with other sulfosalts and sulfides. It most commonly co-occurs with quartz, galena, sphalerite, chalcopyrite, pyrite, arsenopyrite, and other rarer sulfosalts from the lillianite group, such as gustavite and pavonite. ## Localities The only confirmed occurrence (type locality) of staročeskéite in the world is the historic silver and polymetallic mine in Kutná Hora, Czech Republic. The mineral was found in mine dumps originating from former exploitation.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of staročeskéite specimens is assessed primarily based on the abundance and size of the crystals, although these remain microscopic. The most desirable specimens are those where well-formed, though tiny, needles or aggregates are visible against a contrasting quartz matrix. Crucially, confirmation of the mineral's identification by a reputable laboratory significantly enhances the scientific and collector value of the specimen. ## Popular Localities The only source of specimens is the type locality – Kutná Hora in the Czech Republic. Specimens from this location that are properly documented are the only authentic ones on the collector's market.

Care and storage

## Cleaning Staročeskéite specimens are extremely delicate and usually occur as microscopic inclusions in the host rock (quartz). No mechanical or chemical cleaning is recommended, as this could irreversibly damage the tiny crystals. It is best to leave the specimen in its untouched state. ## What to Avoid Avoid contact with chemicals, acids, and ultrasound. As a sulfosalt, the mineral may be sensitive to oxidation and changes in humidity. It should be protected from dust and moisture. ## Storage It is recommended to store specimens in closed, stable containers (e.g., "perky boxes") to protect them from mechanical damage, dust, and humidity fluctuations. Display should be away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)