Buynite

Chemical formula: Tl₁+Pb₂+₁₄As₃+₁₇S₂-₄₀

Buynite is an extremely rare, newly discovered lead, thallium, and arsenic sulfosalt, forming microscopic, metallic crystals.

## Characteristics Buynite is a mineral from the sulfosalt group, first described in 2023. It occurs as extremely small, acicular or bladed crystals, reaching up to 200 micrometers in length and only a few micrometers in thickness. These crystals are elongated and often exhibit striations. Due to their microscopic size, visual features are only discernible under high magnification. The mineral has a metallic luster and is opaque. ## Physical Properties Due to the microscopic size of the crystals, many physical properties of buynite, such as hardness, density, cleavage, or fracture, have not yet been precisely determined. The calculated density is 5.73 g/cm³. The luster is metallic, and the streak is black. ## Colors and Varieties Buynite has a black color. In reflected light under a microscope, its color is white with a delicate, greenish-yellow tint. No varieties have been distinguished. ## History and Name The mineral is named in honor of Dr. Robert A. Buyn (born 1944), an American mineralogist and curator of collections at the Natural History Museum of Los Angeles County, in recognition of his contributions to sulfosalt mineralogy. The mineral was approved by the International Mineralogical Association (IMA) in 2023 (IMA2023-051). The discovery was made based on the analysis of material from the Lengenbach quarry in Switzerland. ## Uses Buynite, as an extremely rare mineral occurring in microscopic quantities, has no practical application. It is solely an object of scientific and collecting interest for specialized micromount mineral collectors.

Properties

Luster: Metallic
Streak: Black
Density: 5.73
Transparency: Opaque
Crystal system: Triclinic

Diagnostic features

## Identification Identification of buynite is only possible using advanced analytical methods, such as energy-dispersive spectroscopy (EDS) and single-crystal X-ray diffraction (SC-XRD). Visual identification in the field or even under a standard microscope is impossible. Its unique chemical composition and crystallographic parameters are characteristic features. ## Distinguishing from Similar Minerals Buynite occurs in paragenesis with other visually very similar sulfosalts from Lengenbach, such as hutchinsonite, imhofite, wallisite, and bernardite. Distinguishing it from these minerals requires specialized chemical and structural analysis. Its unique crystal structure is a key diagnostic feature. ## Crystal Forms Buynite forms very small, acicular or bladed crystals, elongated along the [100] axis. They reach lengths of up to 200 µm and thicknesses of up to 5 µm. The crystals are often flattened and can form small, loose aggregates.

Geological environment

## Genesis Buynite forms as a result of hydrothermal processes in dolomite deposits. Its occurrence is associated with crystallization from solutions rich in arsenic, lead, thallium, and sulfur at relatively low temperatures. ## Mineral Associations This mineral co-occurs with other rare sulfosalts, which is typical for the Lengenbach locality. It is most often accompanied by hutchinsonite, imhofite, wallisite, bernardite, as well as realgar and orpiment. These minerals crystallize on a dolomite matrix. ## Localities The only confirmed locality of buynite in the world is the Lengenbach quarry in the Binn Valley (Binntal) in the canton of Valais, Switzerland. This is the type locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of buynite primarily depends on the confirmation of its identity through analysis. The most valuable specimens are those with well-formed, though still microscopic, crystals, clearly separated from other minerals and set on an aesthetic dolomite matrix. The quality of documentation confirming the authenticity of the specimen is crucial. ## Popular Localities The only source of buynite specimens is its type locality – the Lengenbach quarry in Switzerland, world-renowned for its rare and unique sulfosalts.

Care and storage

## Cleaning Specimens containing buynite, due to their extreme fragility and microscopic crystal sizes, should not be cleaned mechanically or chemically. Any attempts at cleaning risk irreversible destruction of the mineral. They should be left in their untouched state. ## What to Avoid Avoid any contact with chemicals, ultrasound, and sudden temperature changes. The crystals are extremely brittle and sensitive to vibrations and shocks. They should not be exposed to strong light, which could cause thermal changes. ## Storage Specimens should be stored exclusively in specialized "micromount" boxes, which protect them from dust, moisture, and mechanical damage. Store in stable temperature conditions, away from sources of vibration.

Sources

IMA Mineral List (CNMNC)