Rhodplumsite

Chemical formula: Rh₃Pb₂S₂

Rhodplumsite is a very rare lead rhodium sulfide, forming tiny, hexagonal crystals with a metallic luster.

## Characteristics Rhodplumsite is an extremely rare mineral from the sulfide group, composed of rhodium, lead, and sulfur. It occurs as very small, hexagonal, tabular crystals, usually not exceeding 0.2 mm in size. It is observed as inclusions in other minerals, mainly in platinum-group element alloys. It has a steel-gray color and a metallic luster. ## Physical Properties Due to its extreme rarity and small crystal size, many physical properties of rhodplumsite have not been fully investigated. Its Mohs hardness is estimated at approximately 3.5. The mineral is opaque, and its density, calculated based on its chemical formula and unit cell parameters, is 9.31 g/cm³. ## History and Name The mineral's name refers to its chemical composition – the dominant elements: rhodium (Latin: *rhodium*) and lead (Latin: *plumbum*). It was first described in 1982 by T.L. Evstigneeva, A.D. Genkin, V.A. Kovalevkera, N.V. Trubkin, and A.I. Tsepin. The type locality (*locus typicus*) was recognized as the gabbro-norite intrusion near the Chainety River in the Koryak-Kamchatka massif in the Russian Far East.

Properties

Mohs hardness: 3.5
Color: Gray
Luster: Metallic
Streak: Black
Density: 0
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of rhodplumsite is only possible using advanced laboratory techniques, such as electron microprobe analysis (EDS/WDS) to confirm chemical composition and X-ray diffraction (XRD) to determine crystal structure. Visual identification is impossible due to its microscopic size and similarity to other metal sulfides. ## Differentiation from similar minerals Under a reflected light microscope, rhodplumsite may be confused with other platinum-group element or lead sulfides. Definitive differentiation requires specialized chemical analysis. ## Crystal forms It forms very small, hexagonal, tabular crystals.

Geological environment

## Genesis Rhodplumsite forms in ultramafic igneous rocks, particularly in dunites and pyroxenites, which have undergone serpentinization. It is a hydrothermal mineral, crystallizing in the late stages of the formation of platinum-group element deposits. ## Mineral associations This mineral coexists with other platinum-group minerals and sulfides. It is most commonly associated with: chalcopyrite, bornite, heazlewoodite, irarsite, cuprorhodsite, cuproiridsite, malanite, as well as native osmium, iridium, and ruthenium. ## Localities Confirmed occurrences of rhodplumsite are extremely rare and limited to a few locations worldwide. Besides the type locality in Russia (Koryak-Kamchatka massif), it has been identified in platinum-group element deposits in the Bushveld Complex in South Africa, in the Yubdo district in Ethiopia, and in the Kalatong Ni-Cu-PGE deposit in Xinjiang, China.

Rarity

Extremely rare

For collectors

## Quality criteria From a collector's perspective, the only value is the mere fact of possessing a confirmed specimen with this mineral. Since it occurs as microscopic inclusions, its aesthetic qualities are zero. The most valuable specimens are those in which rhodplumsite is well-isolated, identifiable on a polished section, and comes from a well-documented locality, especially the type locality.

Care and storage

## Cleaning Due to its extreme rarity and microscopic size, rhodplumsite specimens are practically not subject to cleaning. They are preserved in the state in which they were found, most often as inclusions in polished rock sections. ## What to avoid Avoid any mechanical manipulation, abrasion, and contact with chemicals that could damage the delicate crystals or the surrounding rock matrix. ## Storage Specimens containing rhodplumsite should be stored in specialized "micromount" boxes, protecting them from dust, moisture, and mechanical damage. Observation is only possible under a microscope.