Arsenquatrandorite

Chemical formula: Ag₁+₁₇.₆Pb₂+₁₂.₈Sb₃+₃₈.₁As₃+₁₁.₅S₂-₉₆

Arsenquatrandorite is a rare sulfosalt mineral, an arsenic analogue of quatrandorite, occurring as microscopic grains.

## Characteristics Arsenquatrandorite is a very rare sulfosalt mineral, approved by the IMA in 2015. It is the arsenic analogue of quatrandorite (andorite IV). It occurs as anhedral (irregular) grains up to 200 micrometers in size, usually intergrown with other sulfosalts. Observed in reflected light, it is white to gray, with a creamy tint. It exhibits weak pleochroism and anisotropy. ## Physical Properties Due to the microscopic size of the grains, most physical properties, such as hardness, density, luster, or transparency, have not been precisely determined. The density was calculated based on the chemical formula and unit cell parameters and is 5.45 g/cm³. ## History and Name The mineral's name refers to its chemical composition – it is an arsenic (Arsen-) analogue of quatrandorite (-quatrandorite). It was discovered in the Quiruvilca deposit in Peru and described by Dan Top, Emil Makovicky, Chris J. Stanley, Tonci Balic-Zunic, and William G. Mumme. It was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2015 (IMA2015-068). ## Uses Arsenquatrandorite has no industrial application. It is of purely scientific interest and is an object of interest for specialized collectors of rare minerals (so-called micromounts).

Properties

Luster: Metallic
Streak: Black
Density: 5.45
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of arsenquatrandorite is impossible without advanced laboratory techniques. It requires chemical analysis (e.g., using an electron microprobe - EDS/WDS) and X-ray diffraction (XRD) studies to confirm the crystal structure. In reflected light under a polarizing microscope, it exhibits weak anisotropy and pleochroism. ## Distinguishing from similar minerals It is practically impossible to visually distinguish it from other lead, silver, antimony, and arsenic sulfosalts, such as quatrandorite, andorite VI, uchucchacuaite, or owenite. Differentiation is based solely on precise analysis of the As to Sb ratio and structural parameters. ## Crystal forms This mineral has only been observed in the form of anhedral (irregular, xenomorphic) grains not exceeding 200 micrometers in size.

Geological environment

## Genesis Arsenquatrandorite forms as a result of hydrothermal processes in polymetallic veins. In the type locality (Quiruvilca), it forms in the late stages of crystallization, replacing earlier sulfosalts. ## Mineral associations This mineral co-occurs with other sulfosalts, such as uchucchacuaite, owenite, andorite VI, as well as with pyrite, quartz, enargite, and barite. ## Localities The only confirmed and described locality of arsenquatrandorite in the world is its discovery site – the Quiruvilca mine, in the province of Santiago de Chuco, in the La Libertad region of Peru.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic mineral, the collector's value of arsenquatrandorite is mainly related to its extreme rarity and scientific significance. A specimen is a fragment of rock (matrix) containing analytically confirmed mineral grains. Samples in which arsenquatrandorite grains are relatively "rich" and well-exposed in association with other rare sulfosalts from this locality are most highly valued. ## Popular localities The only source of specimens is the Quiruvilca mine in Peru, which is the type locality for many other rare sulfosalts.

Care and storage

## Cleaning Specimens of this mineral occur as microscopic grains within the host rock and do not require cleaning. Any attempt at mechanical or chemical cleaning may destroy the delicate grains. ## What to avoid Avoid contact with chemicals, ultrasound, and sudden temperature changes. As a sulfosalt, it may be susceptible to oxidation in a humid environment. ## Storage Specimens containing arsenquatrandorite (micromounts) should be stored under stable conditions, in sealed, dry containers (e.g., micromount boxes), away from dust, light, and moisture.

Sources

IMA Mineral List (CNMNC)