Reckibachite

Chemical formula: Ag₁+₂Pb₂+₁₂As₃+₁₄Sb₃+₄S₂-₄₀

Reckibachite is a very rare, lead-gray sulfosalt mineral with a metallic luster, occurring as tiny, acicular crystals.

## Characteristics Reckibachite is a complex sulfosalt of lead, silver, arsenic, and antimony. It forms very fine, acicular or hair-like crystals, which usually occur as tangled aggregates or crusts on the host rock. Individual crystals are rarely visible to the naked eye. The mineral has a lead-gray to steel-gray color and a metallic luster. ## Physical Properties Due to the small size of the crystals, most physical properties, such as hardness, density, or cleavage, have not been precisely determined. The crystals are opaque and exhibit a strong, metallic luster. The streak is black. ## Colors and Varieties The mineral is uniform in color, occurring in shades of lead-gray or steel-gray. No varieties are distinguished. ## History and Name Reckibachite was recognized as a new mineral species by the International Mineralogical Association (IMA) in 2018. Its name comes from the discovery locality in the Reckibach valley, in the Binn region of Switzerland, which is known for the occurrence of unique and rare sulfosalt minerals. It was described by a team of mineralogists, including Stefan Graeser, who has made significant contributions to the study of the mineralogy of this region. ## Uses Reckibachite has no industrial applications. Its significance is purely scientific and collectible, being an object of interest for specialists in rare sulfosalts and systematic mineralogy.

Properties

Luster: Metallic
Streak: Black
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of reckibachite in the field or based on appearance is practically impossible. It requires advanced analytical techniques, such as electron microprobe (EDS/WDS) to determine chemical composition and X-ray diffraction (XRD) to confirm crystal structure. Visually, it can be suspected in samples from the type locality, where it forms characteristic, fine, acicular aggregates with a metallic luster. ## Distinguishing from Similar Minerals Reckibachite is visually indistinguishable from many other rare lead, arsenic, and antimony sulfosalts that often co-occur with it in the Binn valley, such as hutchinsonite, wallisite, sartorite, or baumhauerite. Certain distinction is only possible through chemical and structural analysis. ## Crystal Forms The mineral forms very fine, elongated, acicular crystals, often with a cross-section below a few micrometers. These crystals combine into tangled, woolly, or radial aggregates on the surface of dolomitic rocks.

Geological environment

## Genesis Reckibachite forms as a result of low-temperature hydrothermal processes. It crystallizes in fissures and cavities of dolomitic rocks (the so-called "Binn Dolomite"), which have undergone metamorphism under amphibolite facies conditions, and then modified by subsequent hydrothermal solutions rich in sulfur, arsenic, lead, antimony, and silver. ## Mineral Associations This mineral occurs in paragenesis with other rare sulfosalts, which is typical for its locality. It is most often accompanied by realgar, orpiment, hutchinsonite, edenharterite, jentschite, as well as pyrite and sphalerite. It co-occurs with minerals from the sartorite group. ## Localities The only confirmed occurrence of reckibachite in the world is its type locality: the Lengenbach quarry in the Binn valley (Binntal), Valais canton, Switzerland. This is one of the world's most famous sites for rare sulfosalt minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a reckibachite specimen is primarily assessed based on the richness and abundance of aggregates on the rock matrix. Since individual crystals are microscopic, specimens with dense, well-formed clusters of acicular crystals are highly valued. The aesthetics of the entire sample, including contrast with the dolomitic matrix and the presence of well-identified associated minerals, are also important. ## Popular Localities The only source of reckibachite specimens is the Lengenbach quarry in Switzerland. Specimens from this locality are highly prized by specialized collectors of systematic minerals and micromounts.

Care and storage

## Cleaning Due to the extreme delicacy and small size of the crystals, mechanical cleaning is not recommended. If necessary, compressed air can be used from a safe distance to remove loose dust. Avoid contact with water and chemical cleaning agents. ## What to Avoid Avoid contact with all liquids, acids, and bases. The crystals are very brittle and sensitive to mechanical damage, vibrations, and sudden temperature changes. Prolonged exposure to strong light may not be advisable, although there are no detailed studies on this topic. ## Storage Reckibachite specimens should be stored exclusively in stable, sealed "micromount" containers to protect them from dust, moisture, and physical damage. Avoid touching the mineral surface.

Sources

IMA Mineral List (CNMNC)