Plumbopalladinite

Chemical formula: Pb<sub>₂</sub>Pd<sub>₃</sub>

Plumbopalladinite is a rare lead-palladium alloy, occurring as small, metallic grains in ultramafic rocks.

## Characteristics Plumbopalladinite is a very rare mineral from the native alloys group, consisting mainly of lead and palladium. It occurs as small, irregular grains or flakes, usually not exceeding 1 mm in size. Its appearance is typically metallic, with a color ranging from tin-white to steel-gray, often with a yellowish or pinkish tint. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties This mineral is characterized by a strong, metallic luster. It is opaque. Its Mohs hardness is relatively high for a metal alloy, approximately 5. The density is significant due to the presence of lead and palladium, reaching a value of 12.35 g/cm³. ## History and Name Plumbopalladinite was first described in 1970 by A.D. Genkin, T.L. Evstigneeva, L.N. Vyal'sov, I.P. Laputina, and N.V. Troneva. Its name is derived from the Latin words *plumbum* (lead) and *palladium*, directly referring to its chemical composition. The type locality (place of first discovery) was identified as a gabbro-norite intrusion in the Talnakh region, near Norilsk in Siberia, Russia.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Gray
Density: 12.35
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Identification of plumbopalladinite in the field is practically impossible. It requires advanced laboratory methods, such as reflectivity analysis in reflected light (characteristic creamy-pink color) and chemical composition analysis using an electron microprobe (EDS/WDS). Its high density and metallic luster are indicators, but not sufficient for definitive identification. ## Distinguishing from Similar Minerals It can be confused with other platinum-group minerals (PGMs) such as palladinite, kotulskite, majakite, or native palladium. Differentiation requires specialized analytical studies, as all these minerals occur as small, metallic grains with a similar appearance. ## Crystal Forms Plumbopalladinite forms irregular, anhedral (lacking well-developed faces) grains and flakes, often intergrown with other palladium and platinum minerals. Well-formed crystals are not observed.

Geological environment

## Genesis Plumbopalladinite forms as a result of magmatic processes within differentiated intrusions of ultramafic and mafic rocks, such as dunites, peridotites, and gabbronorites. It crystallizes from late, platinum-group element and sulfide-rich magmatic melts. ## Mineral Associations It most commonly co-occurs with other platinum-group minerals, such as kotulskite, polarite, sobolevskite, sperrylite, as well as with chalcopyrite, pentlandite, cubanite, and magnetite. ## Localities The most important and classic locality for this mineral is the copper-nickel deposits in the Norilsk-Talnakh region on the Putorana Plateau (Siberia, Russia). It has also been reported in the Bushveld Complex in South Africa, Sudbury in Canada, and several other ultramafic intrusions worldwide where platinum-group metals are mined.

Rarity

Very rare

For collectors

## Quality Criteria As a "micromount" type mineral, the collector's value of plumbopalladinite is primarily dependent on the confirmation of its identity through chemical analysis. The most prized specimens are those in which the plumbopalladinite grains are relatively large (for this mineral, i.e., close to 1 mm), clearly visible, and identified within a polished rock sample (a "polished section"). Association with other rare platinum-group minerals also increases the specimen's value.

Care and storage

## Cleaning Due to the extreme rarity and small size of specimens, mechanical cleaning is highly inadvisable. It usually occurs as inclusions in other minerals and does not require separate cleaning. If necessary, compressed air can be used to remove dust. ## What to Avoid All chemicals, especially acids, can damage or destroy the mineral. Ultrasound and sudden temperature changes should be avoided. It should not be subjected to any hardness tests that could damage the small grains. ## Storage Plumbopalladinite specimens should be stored in stable conditions, in sealed "micromount" boxes, to protect them from dust and mechanical damage. Direct exposure to sunlight and moisture should be avoided.

Sources

IMA Mineral List (CNMNC)