Sztrókayite

Chemical formula: Bi<sub>3</sub>TeS<sub>2</sub>

Sztrókayite is a rare bismuth sulfide and telluride, forming tiny, metallic inclusions in quartz veins.

## Characteristics Sztrókayite is a very rare mineral from the sulfosalt group, chemically classified as a bismuth sulfide and telluride. It occurs as very small, acicular or lamellar crystals, usually not exceeding 1 mm in length. Most often, it forms inclusions in quartz ore veins. Visually, it is an opaque mineral with a metallic luster and a steel-gray color. ## Physical Properties This mineral is characterized by a metallic luster. Due to the microscopic size of the crystals, accurate determination of many physical properties, such as hardness or density, is difficult. The density calculated based on the chemical formula and unit cell parameters is approximately 8.11 g/cm³. ## History and Name Sztrókayite was first described in 1999 by S. Koch and G. Vincze. The mineral is named in honor of Kálmán Imre Sztrókay (1907-1992), a Hungarian mineralogist and professor at Eötvös Loránd University in Budapest, for his contributions to Hungarian mineralogy.

Properties

Luster
Metallic
Streak
Black
Density
8.11
Cleavage
Good on {001}
Transparency
Opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of sztrókayite is almost exclusively possible using advanced laboratory methods, such as chemical analysis with an electron microprobe (EDS/WDS) and X-ray diffraction (XRD). Visually, under a microscope, its steel-gray color, metallic luster, and characteristic, fine, acicular forms can be observed. ## Differentiation from similar minerals Sztrókayite can be confused with other bismuth sulfosalts, such as bismuthinite, tetradymite, or tellurobismuthite, with which it often co-occurs. Certain differentiation requires chemical composition analysis, confirming the simultaneous presence of bismuth, tellurium, and sulfur in appropriate proportions. ## Crystal forms It forms very fine, acicular or lamellar crystals, usually up to 1 mm long and several tens of micrometers wide. These crystals occur as single inclusions or form small, tangled aggregates.

Geological environment

## Genesis Sztrókayite forms under hydrothermal conditions, in low-temperature quartz-ore veins. Its presence is associated with tellurium-bismuth mineralization. ## Mineral associations This mineral co-occurs with other tellurides and sulfides. In the type locality (Nagybörzsöny mine), it was found in association with native bismuth, bismuthinite, tetradymite, tellurobismuthite, pyrite, quartz, and carbonates. ## Localities The only confirmed and described locality of sztrókayite in the world is its discovery site – the Felső-Rózsa mine in Nagybörzsöny, in the Börzsöny Mountains, Hungary.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic mineral, sztrókayite is not evaluated according to typical criteria such as size or color. The collector's value of a specimen lies in its confirmed authenticity, the abundance of its occurrence on the rock matrix, and the quality of associated minerals. The most valuable samples are those with well-formed, though still microscopic, crystals whose identity has been analytically confirmed. ## Popular localities The only source of specimens is the historic Felső-Rózsa mine in Nagybörzsöny, Hungary. Material from this locality is extremely rare on the collector's market.

Care and storage

## Cleaning Due to the extremely small size and fragility of the crystals, mechanical cleaning is neither recommended nor usually possible. Specimens should be protected from dust. ## What to avoid Avoid contact with chemicals that could react with sulfides and tellurides. Due to its brittleness, avoid any shocks and impacts. Store away from moisture to prevent oxidation. ## Storage Sztrókayite specimens, typically as microscopic inclusions in the host rock, are best stored under stable conditions, in sealed "micromount" boxes, which protect them from dust, moisture, and mechanical damage.

Sources

Read more