Permingeatite

Chemical formula: Cu₃SbSe₂-₄

Permingeatite is a very rare copper selenoantimonide, forming tiny, metallic grains in association with other selenides.

## Characteristics Permingeatite is a very rare mineral from the sulfosalt group, specifically a copper selenoantimonide. It occurs as very fine, anhedral (irregular) grains, usually not exceeding 0.1 mm in size. These grains are dispersed within a mass of other minerals, mainly uraninite. Due to its microscopic size, its visual features are difficult to observe without specialized equipment. In polished sections under a reflected light microscope, it has a grayish-white color with a slight pinkish tint. ## Physical Properties As an opaque mineral with a metallic luster, permingeatite is characterized by high density. Its hardness has not been precisely measured, but it is estimated to be around 3.5-4 on the Mohs scale. It does not exhibit cleavage, and its fracture is uneven. It is a brittle mineral. ## Colors and Varieties The observed color of permingeatite is steel-gray to black. In reflected light, its grayish-white color with a pinkish or purplish tint is revealed. No color varieties or commercial forms are known. ## History and Name The mineral was first described in 1971 by Zdeněk Johan, Paul Picot, Francoise Ruhlmann, and Cestmir Hak. Its name commemorates François Permingeat (1917-1988), a French mineralogist and professor at the University of Toulouse, in recognition of his contributions to the study of ore minerals. The type locality (locus typicus) is the Předbořice uranium deposit in the Czech Republic. ## Uses Permingeatite has no industrial or commercial applications. Its significance is purely scientific and collectible, although due to its extreme rarity and microscopic size, it is an object of desire only for specialized collectors of rare minerals.

Properties

Mohs hardness: 3.5-4
Luster: Metallic
Streak: Black
Density: 5.96
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Identification of permingeatite is possible only with advanced laboratory techniques. In polished sections, under an ore microscope in reflected light, it can be preliminarily identified based on its grayish-white color with a pinkish tint, lack of pleochroism, and anisotropy. Final confirmation requires chemical analysis (e.g., electron microprobe - EDS/WDS) to determine its composition (presence of copper, antimony, and selenium in appropriate proportions) and structural analysis (X-ray diffraction - XRD). ## Distinguishing from Similar Minerals Permingeatite can be confused with many other fine, gray sulfosalts and selenides, such as tetrahedrite, tennantite, hakite, or berzelianite. Distinguishing it from hakite (with which it forms a series) is particularly difficult and requires precise chemical analysis. Visually, without specialized studies, it is practically impossible to distinguish. ## Crystal Forms This mineral forms only very fine, anhedral (irregular) grains, most often with a diameter of less than 0.1 mm. It has not been observed in the form of well-developed crystals.

Geological environment

## Genesis Permingeatite is a hydrothermal mineral. It forms under low-temperature conditions, in calcite-selenide veins cutting uranium deposits. At the type locality (Předbořice), it formed as a result of crystallization from selenium-rich solutions that interacted with earlier ore minerals. ## Mineral Associations This mineral occurs in close association with other selenides and sulfides. It is most often accompanied by: uraninite (as the matrix mineral), berzelianite, umangite, eskebornite, clausthalite, klockmannite, hakite, tetrahedrite, chalcopyrite, and calcite and dolomite as vein minerals. ## Localities Permingeatite is an extremely rare mineral, identified in only a few locations worldwide. The most important and confirmed localities are: * **Czech Republic:** Předbořice, near Kovářov - the type locality (locus typicus), where it occurs in calcite veins within a uranium deposit. * **Argentina:** El Tolar deposit, La Rioja province.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a permingeatite specimen is not assessed based on aesthetic criteria such as color or form, as the mineral is microscopic. The key factor is the confirmation of its presence through analysis. For specialized collectors (so-called "micromounters" or collectors of rare minerals), any specimen with reliably identified permingeatite is valuable, especially if accompanied by other rare selenides. Samples from the type locality are the most prized. ## Popular Localities The only source of specimens that may occasionally appear on the specialized market is the historical type locality in Předbořice, Czech Republic. Finding new material is practically impossible, and specimens come from old research collections.

Care and storage

## Cleaning Due to its microscopic size and occurrence as inclusions in other minerals, independent cleaning of individual permingeatite grains is impossible and impractical. Specimens containing permingeatite should be treated according to the requirements of the matrix mineral (e.g., uraninite). ## What to Avoid Avoid abrasion, scratches, and contact with strong chemicals that could damage both permingeatite and associated minerals. Specimens from Předbořice may contain uraninite, which necessitates caution due to radioactivity. ## Storage Specimens with permingeatite, typically polished sections for microscopic examination or rock fragments, should be stored in stable conditions, in specialized boxes (e.g., "micromount" type), protected from dust and mechanical damage. If uraninite is an associated mineral, the specimen should be stored away from radiation-sensitive materials and in a well-ventilated area.

Sources

IMA Mineral List (CNMNC)