Menshikovite

Chemical formula: Pd₃Ni₂As₃

An intermetallic palladium nickel arsenide, forming microscopic, hexagonal crystals with a metallic luster.

## Characteristics Menshikovite is a very rare mineral from the arsenide group, being a natural alloy (intermetallic compound) of palladium, nickel, and arsenic. It occurs as extremely small, hexagonal or trigonal grains, usually not exceeding 0.2 mm in size. It is observed as inclusions in other minerals, most often in alloys of platinum-group metals. Its crystals have a metallic luster and are opaque. ## Physical Properties Due to the microscopic size of its crystals, many physical properties of menshikovite have not been precisely determined. Hardness is estimated at approximately 5 on the Mohs scale. The mineral is characterized by a high density, around 9.45 g/cm³, which is typical for compounds containing heavy metals such as palladium. ## Colors and Varieties The mineral is gray to white with a yellowish tint in reflected light. No varieties have been distinguished. ## History and Name The mineral is named in honor of Mikhail Mikhailovich Menshikov (1935–2003), a Russian mineralogist from the Geological Institute on the Kola Peninsula, for his contributions to the study of platinum-group minerals. The mineral was approved by the IMA in 2005, and its discovery was described in 2006. The type locality is the Chineisky (Chitinsky) gabbro-wehrlite massif in the Zabaykalsky Krai, Russia. ## Applications Menshikovite has no industrial applications due to its extreme rarity and microscopic size. It is of purely scientific interest and is an object of interest for specialized micromineral collectors.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Black
Density: 9.45
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Identification of menshikovite is possible only through advanced laboratory methods, such as electron microprobe analysis (EDS/WDS) in a scanning electron microscope (SEM) in reflected light. Its high reflectance and characteristic chemical composition are crucial for identification. ## Distinguishing from Similar Minerals It can be confused with other microscopic arsenides and platinum-group metal alloys, such as majakite (PdNiAs), sperrylite (PtAs₂), or palladoarsenide (Pd₂As). Differentiation requires precise chemical analysis, as all these minerals have a similar appearance (whitish or gray grains with a metallic luster). ## Crystal Forms Menshikovite forms very small, anhedral or subhedral grains. Hexagonal crystal outlines are rarely observed.

Geological environment

## Genesis Menshikovite forms in ultramafic and mafic magmatic intrusions, in zones rich in sulfides and platinum-group elements (PGE). It crystallizes in the late stages of magmatic processes, under conditions of low sulfur activity, which favors the formation of arsenides instead of sulfides. ## Mineral Associations This mineral co-occurs with other PGE minerals, such as stibiopalladinite, majakite, sperrylite, native platinum, as well as chalcopyrite, pentlandite, pyrite, chromite, and magnetite. ## Localities The only confirmed locality for menshikovite worldwide is its type locality: the copper and PGE deposit in the gabbro-wehrlite intrusion of the Chineisky (Chitinsky) massif, in the Zabaykalsky Krai, Siberia, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of menshikovite is solely related to its presence on the specimen and analytical confirmation. The most valuable specimens are those where menshikovite grains are relatively "large" (above 0.1 mm) and clearly visible in association with other rare PGE minerals. The specimen must originate from the type locality and ideally be part of the material studied in the original publication. ## Popular Localities The only source of specimens is the Chineisky massif in Russia. Collector material is practically unavailable on the open market and is mainly found in institutional collections and with specialized collectors who obtained it directly from researchers.

Care and storage

## Cleaning Specimens containing menshikovite, typically polished sections or rock fragments, do not require cleaning. Any attempts at mechanical or chemical cleaning may damage the microscopic mineral grains. ## What to Avoid Avoid contact with chemicals, acids, and ultrasound. Do not heat specimens. As an arsenic-containing mineral, dust generated during any processing is toxic. ## Storage Specimens should be stored under stable conditions, in sealed "micromount" boxes, to protect them from dust and mechanical damage. It is best to store them in a dry place, away from direct sunlight.

Sources

IMA Mineral List (CNMNC)