Dekatriasartorite

Chemical formula: Tl₁+Pb₂+₅₈As₃+₉₇S₂-₂₀₄

Dekatriasartorite is a very rare, lead-gray lead, arsenic, and thallium sulfosalt, forming tiny, needle-like crystals.

## Characteristics Dekatriasartorite is a very rare mineral from the sulfosalt group, chemically classified as a complex lead, arsenic, and thallium sulfosalt. It occurs as very small, acicular or hair-like crystals, which can form tangled aggregates. Its color is lead-gray, and due to the small size of the crystals, detailed visual features are difficult to observe without a microscope. ## Physical Properties This mineral is characterized by a metallic luster. Its crystals are opaque. Due to its extreme rarity and small sample sizes, full data regarding physical properties such as hardness or density have not yet been fully investigated and published. ## Colors and Varieties Dekatriasartorite occurs in a uniform, lead-gray color. No color or commercial varieties are known. ## History and Name The mineral's name comes from the Greek words "deka" (ten), "tria" (three), and "sartor," referring to its structural and chemical relationship with sartorite and its crystallographic parameters. It was formally described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2008. ## Applications Dekatriasartorite has no industrial application. Its significance is purely scientific and collectible, being an object of interest for specialized research institutions and collectors of rare minerals.

Properties

Luster: Metallic
Streak: Black
Cleavage: Perfect on {010}
Transparency: Opaque
Crystal system: Triclinic

Diagnostic features

## Identification Identification of decatriasartorite is almost exclusively possible using advanced laboratory methods, such as X-ray structural analysis (XRD) and chemical microanalysis (EDS/WDS). Visual identification in the field or even in a collection is impossible due to its appearance, which is almost identical to many other sulfosalts from Lengenbach. ## Distinguishing from Similar Minerals This mineral is virtually indistinguishable visually from other rare lead and arsenic sulfosalts found in the same locality, such as sartorite, dufrénoysite, baumhauerite, or rathite. Certain differentiation requires specialized chemical and structural analysis. ## Crystal Forms Dekatriasartorite forms very fine, elongated, acicular crystals, often with a rod-like cross-section. These crystals rarely exceed fractions of a millimeter in length and can occur as single needles or form tangled, woolly aggregates on the surface of the matrix rock.

Geological environment

## Genesis Dekatriasartorite forms as a result of hydrothermal processes in ore deposits embedded in metamorphic rocks, such as dolomitic marbles. Its formation is associated with the presence of solutions rich in lead, arsenic, thallium, and sulfur. ## Mineral Associations This mineral occurs in association with other, often equally rare, sulfosalts. It most commonly co-occurs with realgar, sartorite, dufrénoysite, baumhauerite, rathite, and tennantite. These minerals crystallize on a substrate of white, sugary dolomite. ## Localities The only confirmed locality for decatriasartorite in the world is the Lengenbach quarry in the Binn Valley (Binnatal) in the canton of Valais, Switzerland. This is the type locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a decatriasartorite specimen is primarily assessed based on the richness and quantity of crystals on the matrix, rather than their individual size, which is always microscopic. The most prized specimens are those with clearly visible, though tiny, aggregates of acicular crystals, well-contrasted against the white dolomitic matrix. Association with other rare minerals from this locality is also important. ## Popular Localities The only source of decatriasartorite specimens is the Lengenbach quarry in Switzerland. This is one of the world's most famous localities for rare sulfosalts, and specimens from there are highly valued by collectors specializing in systematic minerals and micromounts.

Care and storage

## Cleaning Due to its extreme delicacy and rarity, decatriasartorite specimens should not be cleaned mechanically or chemically. Any contaminants are best removed with compressed air (from a safe distance) or left untouched. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and sudden temperature changes. The mineral is very brittle and sensitive to oxidation. It should not be touched with bare hands. ## Storage Specimens should be stored under stable conditions, in closed, airtight containers (e.g., "micromount" boxes), away from light, moisture, and contaminants. It is best to store them on their original matrix rock to minimize the risk of damage.

Sources

IMA Mineral List (CNMNC)