Lechnerite

Chemical formula: Ag₁+₁₀Cu₁+₄Hg₂+Pb₂+₃₃Sb₃+₅₈S₂-₁₂₈

Lechnerite is an extremely rare lead-antimony sulfosalt with admixtures of silver, copper, and mercury, discovered in Austria.

## Characteristics Lechnerite is a very rare mineral from the sulfosalt group, characterized by a complex chemical composition containing lead, antimony, silver, copper, and mercury. It occurs as small, anhedral (not exhibiting external crystalline forms) grains, not exceeding 100 micrometers in size. These grains are intergrown with other minerals, mainly galena. Due to its microscopic size and mode of occurrence, the visual characteristics of macroscopic specimens are unknown. ## Physical Properties This mineral is opaque and exhibits a metallic luster. Its hardness and density have not been precisely measured due to the size and mode of occurrence of the grains. The calculated density is 5.75 g/cm³. ## Colors and Varieties In reflected light, lechnerite is white to creamy. It does not exhibit pleochroism or internal reflections. No varieties are known. ## History and Name The mineral was discovered in the historic silver and lead mine "Knappenstube" in the Hochtor valley, in the Goldberg massif, in the Hohe Tauern (Salzburg, Austria). It was approved by the International Mineralogical Association (IMA) in 2019 (number 2019-027). The name "lechnerite" honors the Austrian mineral collector, Franz Lechner (1933–2018), who made a significant contribution to the documentation of the mineralogy of the Tauern region.

Properties

Luster: Metallic
Density: 5.75
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of lechnerite is only possible using advanced laboratory methods, such as electron microprobe analysis (EMPA) to determine chemical composition and X-ray diffraction (XRD) to confirm crystal structure. In reflected light under a polarizing microscope, it is weakly anisotropic. ## Distinguishing from Similar Minerals Under the microscope, it can be confused with other lead-antimony sulfosalts, such as plagionite, semseyite, or jamesonite. Chemical analysis is decisive, revealing the presence of silver, copper, and mercury in characteristic proportions. ## Crystal Forms Lechnerite occurs exclusively as anhedral, irregular grains up to 100 µm in size, most often intergrown with galena.

Geological environment

## Genesis Lechnerite forms as a result of hydrothermal processes in Alpine-type ore veins. Its presence has been noted in paragenesis with quartz, galena, and other sulfosalts. ## Mineral Associations This mineral co-occurs with galena, plagionite, semseyite, jamesonite, sphalerite, pyrite, chalcopyrite, and quartz. ## Localities The only confirmed locality of lechnerite in the world is its type locality: the historic "Knappenstube" mine in the Hochtor valley, in the Goldberg massif, in the Hohe Tauern, in the state of Salzburg, Austria.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, lechnerite is not evaluated according to typical collector criteria such as size, color, or crystal form. The value of a specimen lies in its scientific significance and the analytically confirmed presence of the mineral in the host rock (so-called micromount). The most valuable specimens are those from the type locality, with the richest association of other rare sulfosalts.

Care and storage

## Cleaning Due to the microscopic size of grains intergrown within the host rock, cleaning individual lechnerite specimens is neither possible nor necessary. Any cleaning applies to the entire rock and should be limited to gentle dust removal, e.g., with a soft brush. ## What to Avoid Specimens containing lechnerite should be protected from chemicals, especially acids, which can react with sulfides and sulfosalts. Ultrasonic cleaners and rapid temperature changes should be avoided. ## Storage Store in stable conditions, away from moisture and direct sunlight, in a sealed container or display cabinet to prevent dust accumulation and potential chemical reactions.

Sources

IMA Mineral List (CNMNC)