Heyrovskýite

Chemical formula: Pb₂+₆Bi₃+₂S₂-₉

Heyrovskýite is a rare lead bismuth sulfosalt, forming acicular or capillary crystals with a metallic luster.

## Characteristics Heyrovskýite is a mineral from the sulfosalt group, belonging to the lillianite series. It occurs as elongated, acicular or capillary crystals, which can reach several centimeters in length. It often forms tangled aggregates or radial clusters. Its appearance is typical for many sulfosalts – it has a metallic luster and a steel-gray to tin-white color, often with a dull, black tarnish. ## Physical Properties This mineral is opaque and exhibits a strong, metallic luster on fresh surfaces. It is relatively soft, with a Mohs hardness of 3.5. Its density is high, which is characteristic of lead-bearing minerals, and is approximately 7.1 g/cm³. The crystals are flexible, meaning they can be slightly bent without breaking. ## Colors and Varieties Heyrovskýite is steel-gray to tin-white in color. Surfaces exposed to air may become covered with a dull, black or iridescent tarnish. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was first described in 1971 based on samples from Hůrky near Čistá in the Czech Republic. Its name honors Jaroslav Heyrovský (1890–1967), a Czech chemist and inventor, Nobel laureate in Chemistry in 1959 for his discovery and development of polarographic analytical methods. ## Uses Heyrovskýite has no industrial significance. It is solely an object of interest for collectors of rare minerals and scientists studying sulfosalts.

Properties

Mohs hardness: 3.5
Luster: Metallic
Streak: Black
Density: 7.1
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Heyrovskýite can be identified by its characteristic form – long, acicular or capillary crystals, often forming tangled aggregates. Other features include metallic luster, steel-gray color, high density, and flexibility of the crystals. The streak is black. ## Distinguishing from Similar Minerals It can be confused with other acicular sulfosalts, such as jamesonite, boulangerite, or zinkenite. Differentiation often requires advanced analytical methods, such as chemical composition analysis (EDS) or X-ray diffraction (XRD). Jamesonit is more brittle, whereas heyrovskýite is flexible. ## Crystal Forms Crystals are strongly elongated along one axis, forming acicular, capillary, or bladed forms. They usually occur as haphazard, tangled clusters, radial aggregates, or embedded in quartz.

Geological environment

## Genesis Heyrovskýite is a hydrothermal mineral. It forms in medium to high-temperature ore veins, most often in association with metamorphic rocks, such as gneisses, or in quartz veins. ## Mineral Associations It often co-occurs with other sulfides and sulfosalts. The most common associated minerals include galena, bismuthinite, pyrite, chalcopyrite, sphalerite, arsenopyrite, as well as quartz and various carbonates. ## Localities The most important localities worldwide include the discovery site in Hůrky near Čistá in the Czech Republic. Other known localities include the Yaogangxian mine in Hunan Province, China, which yields well-formed specimens, as well as Japan (Ohtani mine), Romania (Băița Bihor), Sweden (Glava), Italy (Elba island), and the United States (Nevada).

Rarity

Rare

For collectors

## Quality Criteria Most valued by collectors are specimens with well-formed, long, and undamaged crystals, forming aesthetic, radial or tangled aggregates. A contrasting association with quartz or other minerals, especially of a different color, significantly enhances the specimen's attractiveness. Luster and absence of tarnish on the surface are also desirable features. ## Popular Localities Specimens from the Yaogangxian mine in China are currently among the most sought after on the collector's market due to their excellent formation and aesthetics. Classic specimens from the Czech type locality are rare and primarily of historical value.

Care and storage

## Cleaning Heyrovskýite specimens are delicate and should be handled with care. To remove dust, it is best to use compressed air or a very soft brush. Wet cleaning, especially with detergents, should be avoided. ## What to Avoid The mineral is sensitive to chemicals, especially acids, which can damage it. It should be protected from moisture and sudden temperature changes. Prolonged exposure to air can cause a dark tarnish to form. ## Storage It is recommended to store specimens in closed, dry containers or display cases to limit air and moisture access. Due to the acicular form of the crystals, avoid placing other minerals on them and protect them from vibrations.

Sources

IMA Mineral List (CNMNC)