Kvačekite

Chemical formula: Ni³⁺(SbSe)³⁻

Kvačekite is an extremely rare nickel seleno-antimonide, discovered in the Czech Republic and known only from one locality worldwide.

## Characteristics Kvačekite is a newly described, extremely rare mineral from the sulfide group and related compounds. It occurs as microscopic, metallic gray grains, most often intergrown with other minerals. Due to its small size and occurrence, visual characteristics are not well known beyond microscopic examination. ## Physical Properties This mineral is opaque and has a metallic luster. Its Mohs hardness is 5-6, and its calculated density is very high at 7.607 g/cm³. The fracture is conchoidal. ## Colors and Varieties Kvačekite has a uniform, gray color. No varieties have been distinguished. ## History and Name The mineral is named in honor of Milan Kvaček (1932-2019), a Czech amateur mineralogist from Tišnov, who was the first to find material containing this new mineral. Kvačekite was officially approved by the International Mineralogical Association (IMA) in 2023 (IMA2023-081). Its discovery was made on material from the Bukov uranium mine in the Czech Republic. ## Uses Kvačekite has no industrial application. Its significance is purely scientific and as a collector's item, as a unique and newly discovered mineral species.

Properties

Mohs hardness
5-6
Luster
Metallic
Streak
grey
Density
7.607
Fracture
Conchoidal
Transparency
Opaque
Crystal system
Isometric

Diagnostic features

## Identification Identification of kvačekite is impossible without advanced laboratory techniques, such as X-ray microanalysis (EDS/WDS) and X-ray diffraction (XRD). Visual identification in the field or in a collection is unfeasible. ## Distinguishing from Similar Minerals This mineral occurs in paragenesis with many other metallic minerals, such as gersdorffite, ullmannite, clausthalite, and penroseite. Distinguishing it from these requires specialized chemical analysis, especially of nickel, antimony, and selenium content. ## Crystal Forms Kvačekite forms only anhedral (irregular) grains, not exceeding a few tens of micrometers in size. No well-formed crystals have been observed.

Geological environment

## Genesis Kvačekite forms as a result of hydrothermal processes. It was found in calcite-uraninite veins cutting metamorphic rocks (biotite gneisses). It is a secondary mineral, likely formed during a late stage of selenide mineralization. ## Mineral Associations This mineral co-occurs with minerals such as: calcite, uraninite, hematite, clausthalite, penroseite, umangite, berzelianite, eskebornite, gersdorffite-krutovite, ullmannite-willyamite, as well as rare selenates (ahlfeldite, schmiederite) and native bismuth. ## Localities The only confirmed locality for kvačekite worldwide is its type locality - the Bukov mine within the Rožná deposit, near the town of Žďár nad Sázavou in the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the only criterion for kvačekite's value is the certainty of its analytical identification and the richness of the mineral association on a given rock fragment. The size of the grains is always microscopic. ## Popular Localities The only source of specimens is the Bukov mine in the Czech Republic. The material comes from historical collections and is not actively acquired.

Care and storage

## Cleaning Due to its extreme rarity and microscopic nature, specimens containing kvačekite should not be cleaned mechanically or chemically. Any attempts at cleaning may irreversibly destroy the mineral. ## What to Avoid Avoid contact with chemicals, ultrasonics, and any form of abrasion. The specimen should be protected from dust and moisture. ## Storage Specimens containing kvačekite should be stored exclusively in specialized "micromount" boxes, protecting them from mechanical damage and contamination. Store in stable room conditions.

External references

Sources

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