Agmantinite

Chemical formula: Ag₁+₂Mn₂+Sn₄+S₂-₄

Agmantynite is an extremely rare sulfide of silver, manganese, and tin, forming microscopic, black grains.

## Characteristics Agmantynite is a sulfide group mineral, identified only in 2018. It occurs as very small, anhedral (irregularly shaped) grains, not exceeding 200 micrometers in size. It is usually intergrown with other sulfide minerals. Its color is black, and on fresh surfaces, it exhibits a metallic luster. ## Physical Properties This mineral is opaque. Due to the microscopic size of its crystals, hardness has not been precisely determined. The density calculated based on chemical composition and crystal structure is approximately 4.91 g/cm³. ## Colors and Varieties Agmantynite is uniform in color – it occurs exclusively in black. No varieties are distinguished. ## History and Name The name "agmantynite" is an acronym derived from the mineral's components: silver (**Ag**), **man**ganese (**Mn**), and **tin** (Sn). It was officially approved by the International Mineralogical Association (IMA) in 2018 (IMA2018-117). Its discovery and description are the result of research conducted on material from the Uchucchacua polymetallic deposit in Peru. ## Applications Due to its extreme rarity and microscopic size, agmantynite has no industrial application. It is of purely scientific significance and is an object of interest for specialized collectors of rare minerals (so-called micromounts).

Properties

Luster: Metallic
Streak: Black
Density: 4.91
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Identification of agmantynite is possible only using advanced laboratory methods, such as X-ray microanalysis (EDS/WDS) in conjunction with X-ray diffraction (XRD). Under collecting conditions, without specialized equipment, it is impossible to identify. ## Distinguishing from Similar Minerals In the form of microscopic grains, it is visually indistinguishable from many other black, metallic sulfides and sulfosalts with which it co-occurs, such as hocartite, pirquitasite, or miargyrite. Certain distinction requires chemical analysis. ## Crystal Forms It occurs as anhedral, i.e., irregular and shapeless grains, often intergrown with other minerals. No well-formed crystals have been observed.

Geological environment

## Genesis Agmantynite forms under hydrothermal conditions in polymetallic deposits. Its formation is associated with crystallization from solutions rich in silver, manganese, tin, and sulfur. ## Mineral Associations It occurs in association with other sulfide and sulfosalt minerals. It is most commonly found in association with alabandite, benavidesite, fizélyite, hocartite, miargyrite, pirquitasite, pyroxmangite, rhodochrosite, and uchucchacuaite. ## Localities The only confirmed occurrence of agmantynite in the world (type locality) is the Uchucchacua polymetallic deposit, in Oyon Province, Lima Region, Peru.

Rarity

Extremely rare

For collectors

## Quality Criteria In the case of such a rare mineral occurring in microscopic form, the main criterion is the certainty of specimen identification. The attractiveness is enhanced by the abundance of agmantynite grains on the rock matrix and the presence of rare associated minerals. The size of the grains, although always microscopic, is also important – the larger, the more valuable. ## Market Prices There is no established market for this mineral. Specimens occasionally appear in the offerings of specialized rare mineral dealers, and their price depends on the quality of the analysis and the richness of the specimen. ## Popular Localities The only source of specimens is the Uchucchacua mine in Peru.

Care and storage

## Cleaning Specimens containing agmantynite, due to the microscopic size of the grains, are practically not subject to cleaning. Any attempts at mechanical or chemical cleaning may destroy the mineral. ## What to Avoid Avoid contact with chemicals, acids, and detergents. As a sulfide, it may be sensitive to moisture and oxidation in the long term. It should be protected from extreme temperatures and shocks. ## Storage Specimens with agmantynite (micromounts) should be stored under stable conditions, in closed, dry containers (e.g., "micromount" boxes), away from dust and direct light.

Sources

IMA Mineral List (CNMNC)