Matthiasweilite

Chemical formula: Pb²⁺Te⁴⁺O₃

Matthiasweilite is a rare lead tellurite of bright yellow color, found in the oxidation zones of gold and tellurium deposits.

## Characteristics Matthiasweilite is a lead tellurite that visually presents as aggregates of small, bladed or acicular crystals, rarely exceeding 1 mm in length. These crystals form rosette-like or radial clusters of a bright yellow color. Due to the small size of the crystals, its features are most often observed under a microscope. ## Physical Properties This mineral is characterized by a hardness of 2.5 on the Mohs scale, making it very soft. It has a high density (7.28 g/cm³), typical for lead-bearing minerals. The luster is described as adamantine to resinous. The fracture is conchoidal. ## Colors and Varieties Matthiasweilite occurs in a uniform, bright yellow color. No colored varieties are known. ## History and Name The mineral's name honors Matthias Weil (born 1966), a German mineral collector and photographer specializing in microminerals, who provided the first specimen for research. It was approved as a new mineral species by the IMA in 2019. The type locality is the dump of the Delamar Mine in Lincoln County, Nevada, USA. ## Uses Matthiasweilite has no industrial applications. It is solely of interest to collectors, especially those specializing in microminerals and rare species.

Properties

Mohs hardness
2.5
Luster
Adamantine
Streak
White
Density
7.282
Fracture
Conchoidal
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of matthiasweilite in the field is impossible. In a collection, it is recognized by characteristic, radial aggregates of bright yellow, acicular crystals on a typical quartz matrix. Final confirmation requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other secondary, yellow lead or tellurium minerals, such as fairbankite or plumbotellurite. Differentiation based on visual characteristics is practically impossible and requires laboratory analysis. ## Crystal Forms It forms thin, bladed or acicular crystals that combine into radial or rosette-like aggregates. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Matthiasweilite is a secondary mineral, forming in the oxidation zone of hydrothermal gold and tellurium deposits. It forms as a result of the weathering of primary tellurides in the presence of lead-rich fluids. ## Mineral Associations At the type locality, it co-occurs with quartz, barite, cerussite, anglesite, as well as other rare tellurites and tellurates, such as mcalpineite, quetzalcoatlite, and eztlite. ## Localities The only confirmed occurrence of matthiasweilite in the world is its type locality – the dump of the Delamar Mine in the Delamar Mining District, Lincoln County, Nevada, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The most valuable specimens are those with rich, well-formed, radial aggregates of crystals with an intense, bright yellow color, contrasting with the rock matrix. Due to its microscopic nature, the aesthetics and photogenicity of the specimen under magnification are key. ## Popular Localities The only source of specimens is the Delamar Mine in Nevada, USA. All specimens available on the collector's market come from this single location.

Care and storage

## Cleaning Due to its extreme rarity and delicacy, specimens should not be cleaned mechanically or chemically. If necessary, compressed air can be carefully used to remove dust. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and any cleaning tools. The mineral is very soft and brittle, susceptible to mechanical damage. It should be protected from sudden temperature changes. ## Storage Matthiasweilite specimens, as microminerals, should be stored in specialized, sealed "micromount" boxes that protect them from dust and mechanical damage. Display is only possible under a microscope.

External references

Sources

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