Orishchinite

Chemical formula: Ni₂P

Oryshchenite is an extremely rare nickel phosphide, occurring as microscopic, metallic inclusions in iron meteorites.

## Characteristics Oryshchenite is a mineral with a metallic appearance, occurring as very small, rounded or irregular grains, usually not exceeding 100 micrometers in size. It is observed as inclusions within other meteoritic minerals, mainly kamacite. Due to the microscopic size of the crystals, its visual characteristics are difficult to assess without specialized equipment. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness is estimated to be around 6. The density calculated based on the chemical formula and unit cell parameters is 7.37 g/cm³. ## History and Name Oryshchenite was officially recognized by the International Mineralogical Association (IMA) in 2021. Its name honors Ivan Fedorovich Oryshchenko (1936–2014), a Ukrainian specialist in metallurgy and welding, a professor at the National Technical University of Ukraine. The mineral was discovered in the Dronino iron meteorite, found in 2000 in Russia.

Properties

Mohs hardness: 6
Color: Yellowish-white
Luster: Metallic
Streak: Black
Density: 7.695
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of oryshchenite is possible only with advanced laboratory techniques, such as scanning electron microscopy (SEM) combined with chemical composition analysis (EDS) and electron backscatter diffraction (EBSD). In backscattered electron (BSE) images, its grains are difficult to distinguish from co-occurring schreibersite. ## Distinguishing from Similar Minerals Oryshchenite can be confused with other nickel and iron phosphides found in meteorites, such as schreibersite ((Fe,Ni)₃P) or nickelphosphide ((Ni,Fe)₃P). Final differentiation requires precise analysis of the nickel to phosphorus ratio, which for oryshchenite is 2:1, and confirmation of the crystal structure. ## Crystal Forms Oryshchenite forms anhedral (lacking crystal faces), rounded, or irregular grains ranging from 5 to 100 micrometers in size.

Geological environment

## Genesis Oryshchenite is a mineral of extraterrestrial origin. It forms under extremely reducing conditions within the parent bodies of asteroids from which iron meteorites originate. It crystallizes from a nickel- and phosphorus-rich metallic phase during the very slow cooling of the asteroid's core. ## Mineral Associations This mineral occurs in close association with kamacite (low-nickel iron variety), taenite (high-nickel iron variety), schreibersite, troilite, and graphite. ## Localities The only confirmed locality of oryshchenite in the world (type locality) is the Dronino iron meteorite, found in the Ryazan Oblast, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria Oryshchenite does not occur as standalone collectible specimens. Its value is purely scientific and related to its presence in the meteorite. For meteorite collectors, the value of a specimen (a slice or fragment of the Dronino meteorite) depends on its size, the aesthetics of the etched Widmanstätten pattern, and the presence of rare minerals confirmed by analysis, which significantly increases its price and scientific appeal.

Care and storage

## Cleaning Due to its occurrence as microscopic inclusions within meteorites, isolated cleaning of individual oryshchenite grains is practically impossible and unnecessary. Any cleaning applies to the entire meteorite specimen and should be limited to an absolute minimum, e.g., blowing with compressed air to remove dust. ## What to Avoid Contact of the specimen with chemicals, acids, and moisture should be avoided, as these can lead to corrosion and damage to both oryshchenite and the surrounding metallic matrix (kamacite and taenite). Iron meteorites are susceptible to rusting in humid environments. ## Storage Specimens containing oryshchenite (i.e., fragments of the Dronino meteorite) must be stored under very low humidity conditions, preferably in sealed containers with a desiccant (e.g., silica gel). Display should be in closed display cases with a controlled atmosphere.

External references

https://www.mindat.org/min-53871.html