Palladseite

Chemical formula: Pd<sub>₁₇</sub>Se<sub>₁₅</sub>

Palladseite is a very rare palladium selenide, occurring as microscopic grains with a metallic luster in gold deposits.

## Characteristics Palladseite is an extremely rare mineral from the selenide group, chemically classified as palladium selenide. It forms only microscopic, anhedral grains, usually not exceeding several tens of micrometers in size. In reflected light under a microscope, its color is creamy white, sometimes with a delicate, yellowish tint. It is an opaque mineral with a strong, metallic luster. ## Physical Properties Its Mohs hardness is approximately 5. It has a very high density of 10.36 g/cm³, which is typical for platinum-group element-bearing minerals. It does not exhibit cleavage. It is brittle. ## Colors and Varieties This mineral is uniform in color – always creamy white in microscopic observations. It does not form colored or commercial varieties. ## History and Name It was first described in 1977 by a team of mineralogists (A. D. Genkin, T. L. Evstigneeva, L. N. Vyal'sov, I. P. Laputina, N. V. Troneva) based on material from the Itabira iron ore mine in Minas Gerais state, Brazil. The name directly refers to its chemical composition – the elements palladium (palladium) and selenium (se). ## Uses Palladseite has no industrial applications. Its significance is purely scientific and as a collector's item, as a rare and specific component of some precious metal deposits.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Black
Density: 10.36
Cleavage: None
Transparency: Opaque
Crystal system: Isometric

Diagnostic features

## Identification Identification of palladseite is impossible without specialized equipment. Recognition is based on reflected light analysis (ore microscopy), where its characteristic creamy white color and high reflectivity are observed. Final confirmation requires chemical composition analysis using an electron microprobe (EDS/WDS). ## Distinguishing from Similar Minerals With the naked eye and under a standard microscope, it is impossible to distinguish from other selenides and tellurides of platinum-group metals, such as atheneite, isomertieite, or clausthalite, with which it often coexists. All these minerals form similar, fine, metallic inclusions. ## Crystal Forms Palladseite occurs exclusively as anhedral (irregular) grains. Sometimes it forms irregular rims around native gold grains or other minerals.

Geological environment

## Genesis Palladseite forms as a result of hydrothermal processes in a specific geological environment. Its occurrence is closely associated with hematite-rich metamorphic rocks called "jacutinga," which are a variety of itabirite. Under these conditions, it crystallizes with gold and other ore minerals. ## Mineral Associations It most commonly coexists with native gold, atheneite, isomertieite, potarite, clausthalite, and other rare palladium and mercury selenides. ## Localities The most important and well-documented occurrences of palladseite are in Brazil, in the ore-rich Minas Gerais region (Itabira, Gongo Soco mines) and in Goiás state (Buraco do Ouro gold mine). These are the only confirmed localities of this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, palladseite is not evaluated based on typical aesthetic criteria such as color or form. The value of a specimen lies in the abundance of palladseite grains, their size (though always microscopic), and confirmation of identification by a reputable laboratory. The most valuable samples are those with well-developed associations with other rare minerals, especially gold. ## Popular Localities The only source of collector specimens are the localities in Brazil, of which the historically most important is the Itabira mine in Minas Gerais, which is its type locality.

Care and storage

## Cleaning Specimens containing palladseite, which are usually rock fragments, can be cleaned with a soft brush dry or using distilled water. Due to the microscopic nature of the grains, aggressive mechanical methods that could damage the sample surface should be avoided. ## What to Avoid Avoid contact with strong acids and chemical reagents that could react with palladium selenide or associated minerals. The mineral is stable under normal conditions and is not sensitive to sunlight or temperature changes. ## Storage Storage under standard collector's conditions is fully sufficient. It is recommended to keep specimens in sealed "micromount" boxes to protect them from dust and contamination.

Sources

IMA Mineral List (CNMNC)