Monipite

Chemical formula: MoNiP

Monipite is an extremely rare nickel and molybdenum phosphide, forming microscopic, metallic inclusions in iron meteorites.

## Characteristics Monipite is a mineral from the phosphide group, first described in the Agpalilik iron meteorite, which is a fragment of the larger Cape York meteorite found in Greenland. It occurs as extremely small, anhedral (irregularly shaped) grains, usually not exceeding 100 micrometers in size. It is opaque and has a metallic luster. Its identification requires advanced analytical techniques, such as electron microprobe analysis (EMPA), due to its microscopic size and co-occurrence with other rare phosphides. ## Physical Properties Due to the microscopic size of the grains, most physical properties of monipite have not been precisely measured. Hardness is estimated at approximately 6-7 on the Mohs scale based on comparisons with synthetic analogues and similar minerals. The luster is metallic. The density calculated from the chemical composition and unit cell parameters is 8.35 g/cm³. ## History and Name The mineral name "monipite" refers to its chemical composition – it is an acronym derived from the elements that compose it: molybdenum (Mo), nickel (Ni), and phosphorus (P). It was approved as a new mineral by the International Mineralogical Association (IMA) in 1994 (IMA number 1994-038). It was described by scientists D.I. Biriukov and J.A. Ivanov based on studies of samples from the Agpalilik meteorite.

Properties

Mohs hardness
6-7
Luster
Metallic
Streak
Black
Density
8.35
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification Identification of monipite is impossible without specialized equipment. In a polished meteorite section, under a reflected light microscope, it appears as a bright, creamy-white grain with a metallic luster. Final identification requires chemical composition analysis using an electron microprobe (EMPA) or similar microanalytical techniques. ## Distinguishing from Similar Minerals Monipite co-occurs with other nickel and iron phosphides, such as schreibersite ((Fe,Ni)₃P) and nickelphosphide ((Ni,Fe)₃P), as well as other rare meteoritic minerals. Distinguishing it from these relies solely on precise chemical analysis, which reveals the presence and stoichiometry of molybdenum, nickel, and phosphorus. ## Crystal Forms Monipite forms exclusively anhedral, irregular grains and aggregates, which are inclusions in the metallic mass of the meteorite. No well-formed crystals have been observed.

Geological environment

## Genesis Monipite 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 primary metallic melt (iron-nickel) rich in phosphorus and trace elements such as molybdenum, during the very slow cooling of the asteroid's core. ## Mineral Associations This mineral occurs in paragenesis with the main components of iron meteorites, namely kamacite and taenite (varieties of Fe-Ni alloy). It also co-occurs with other phosphides, mainly schreibersite, as well as with troilite (FeS) and graphite (C). ## Localities The only confirmed locality of monipite on Earth is the Cape York meteorite, specifically its largest fragment named Agpalilik, found in 1963 in northwestern Greenland. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria Monipite does not occur as standalone collector specimens. Its value is purely scientific, and it is an integral, microscopic part of the meteorite in which it was found. For meteorite collectors, the value of a specimen (a slice or fragment) is enhanced by the confirmed presence of such a rare mineral, documented by a scientific institution. Its visual value is zero, as the mineral is invisible to the naked eye.

Care and storage

## Cleaning Specimens containing monipite (typically polished meteorite sections) should only be cleaned with a dry, soft microfiber cloth or compressed air to remove dust. Any contact with water or chemicals is inadvisable. ## What to Avoid Absolutely avoid contact with water, acids, bases, and any chemical agents that could cause corrosion of the metallic meteorite matrix (kamacite and taenite) and monipite itself. Protect the specimen from moisture and sudden temperature changes. ## Storage Meteorite samples with monipite should be stored in a dry environment, preferably in an airtight container with a desiccant (e.g., silica gel). Display should be in a closed cabinet, away from direct sunlight and heat sources.

Sources

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