Hapkeite

Chemical formula: Fe<sub>2</sub>Si

Hapkeite is an extremely rare iron silicide, discovered in the Dhofar 280 meteorite, which formed under highly reducing conditions on the Moon.

## Characteristics Hapkeite is a mineral with a metallic, opaque appearance, occurring as microscopic, elongated or isometric grains ranging from 1 to 30 micrometers in size. It typically forms inclusions within other minerals. Its color in reflected light is yellowish-white, resembling brass. ## Physical Properties Due to the microscopic size of its crystals, most physical properties, such as hardness, density, cleavage, or fracture, have not been precisely measured. The mineral is opaque and exhibits a strong, metallic luster. ## History and Name The mineral's name honors Bruce Hapke, an American planetary scientist from the University of Pittsburgh, who was the first to predict the existence and significance of deposits formed from the gas phase on the surface of lunar regolith grains. Hapkeite was officially approved by the IMA in 2003, and its discovery was made in samples of the Dhofar 280 meteorite, found in Oman in 2000. ## Applications Due to its extreme rarity and microscopic size, hapkeite has no industrial applications. Its significance is purely scientific, providing information about processes occurring on the Moon's surface, and collectible, as a component of unique meteorites.

Properties

Luster
Metallic
Cleavage
None
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Hapkeite identification is possible only through advanced laboratory techniques, such as scanning electron microscopy (SEM) combined with chemical composition analysis (EDS) or electron probe microanalysis (EPMA). In reflected light under a microscope, it is distinguished by its yellowish-white color and strong metallic luster. ## Differentiation from similar minerals It can be confused with other microscopic metallic phases in meteorites, such as kamacite, taenite, schreibersite, or troilite. Definitive differentiation requires chemical composition analysis, which will show the presence of only iron and silicon in a 2:1 ratio. ## Crystal forms It is observed as very small, anhedral (irregular) or subhedral (partially developed) grains, often elongated. It occurs as individual inclusions within other minerals.

Geological environment

## Genesis Hapkeite forms through gas-phase deposition (vapor condensation) under extremely reducing, oxygen-free conditions. This process occurs on the Moon's surface when micrometeorites impact the lunar regolith, locally melting and vaporizing iron- and silicon-rich material. These vapors then rapidly cool and crystallize, forming hapkeite. ## Mineral associations It coexists with minerals typical of lunar regolith, such as ilmenite, anorthite, olivine, pyroxene, as well as native iron (kamacite) and troilite. ## Localities The only confirmed locality for hapkeite is the lunar meteorite Dhofar 280, found in the Dhofar region of Oman. This is an anorthositic breccia regolith, originating from the lunar highlands.

Rarity

Extremely rare

For collectors

## Quality criteria Since hapkeite is a microscopic mineral, it is not evaluated in terms typical for macroscopic specimens. Its collectible value pertains to the entire meteorite specimen in which it has been identified. The most valuable are meteorite fragments with confirmed and well-documented presence of hapkeite, often in the form of polished thin sections or mounts intended for microscopic examination. ## Popular localities The only source of hapkeite on the collector's market is fragments of the Dhofar 280 meteorite. These specimens are extremely rare and sought after by meteorite collectors and scientific institutions.

Care and storage

## Cleaning Specimens (meteorites) containing hapkeite are stable and generally do not require cleaning. Any interventions should be kept to an absolute minimum. If necessary, compressed air can be used to remove dust. ## What to avoid Avoid contact with water, chemicals, and especially acids, which can react with associated minerals. Lunar meteorites should be protected from moisture to prevent oxidation of metallic phases. ## Storage Store in a dry environment, preferably in a sealed container or display case with a desiccant (e.g., silica gel). Avoid sudden temperature changes and direct sunlight.

External references

Sources

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