Halamishite

Chemical formula: Ni<sub>₅</sub>P<sub>₄</sub>

Halamishite is an extremely rare nickel phosphide, forming microscopic, metallic grains within other minerals.

## Characteristics Halamishite is a newly discovered, very rare mineral from the phosphide group. It occurs as extremely small, anhedral (irregularly shaped) grains, usually not exceeding 20 micrometers in size. These grains are most often intergrown with other rare minerals. Due to its microscopic size, visual features visible to the naked eye are not observable; its appearance is known only from electron microscope studies, where it appears as bright, metallic inclusions. ## Physical properties As an opaque mineral, halamishite exhibits a strong, metallic luster. Its hardness and density have not been precisely measured due to its microscopic size and occurrence as inclusions; however, the density calculated based on its chemical formula and unit cell parameters is 7.03 g/cm³. Neither cleavage nor fracture has been observed. ## Colors and varieties In reflected light (under a microscope), halamishite is gray with a slight creamy tint. It does not exhibit pleochroism or internal reflections. No varieties are known. ## History and name The mineral was officially approved by the International Mineralogical Association (IMA) in 2015 under number IMA2015-027. Its name comes from the Hatrurim geological formation in Israel, also known as the "Marl Formation" (in Hebrew "Halamish"), where it was discovered. It was described by mineralogists Evgeny V. Galuskin, Irina O. Galuskina, Yevgeny Vapnik, Polekhovsky Y.S., and Murashko M.N. ## Applications Due to its extreme rarity and microscopic size, halamishite has no practical or commercial applications. It is solely an object of scientific interest and a valuable acquisition for specialized systematic collections, gathering minerals from specific localities or chemical groups.

Properties

Luster: Metallic
Streak: Black
Density: 7.03
Cleavage: None
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of halamishite is impossible without advanced laboratory techniques. It requires chemical composition analysis using an electron microprobe (EDS/WDS) and structural studies by X-ray diffraction (XRD) or electron backscatter diffraction (EBSD). Under a reflected light microscope, it is a gray, metallic mineral. ## Distinguishing from similar minerals It can be confused with other rare nickel phosphides found in the same locality, such as transjordanite (Ni₂P) or negevite (NiP₂). Differentiation relies solely on precise analysis of the nickel to phosphorus ratio in the chemical composition. ## Crystal forms Halamishite forms exclusively microscopic, anhedral grains, most commonly 5 to 20 micrometers in size. They occur as inclusions in transjordanite crystals or at the grain boundaries of diopside and anorthite.

Geological environment

## Genesis Halamishite forms under specific pyrometamorphic conditions, i.e., rock transformations under very high temperature but low pressure. Its formation is associated with the natural combustion of bituminous substances in sedimentary rocks of the Hatrurim formation. This process leads to the formation of a paragenesis of minerals typical of Portland cement, and phosphides, including halamishite, crystallize from local melts rich in phosphorus and metals. ## Mineral associations This mineral occurs in close association with other rare phosphides, primarily transjordanite (Ni₂P) and negevite (NiP₂). It also co-occurs with graphite, diopside, anorthite, and minerals from the larnite-bredigite group. ## Localities The only confirmed locality of halamishite in the world is its type locality: the phosphorite deposit in the Hatrurim basin, in the Negev Desert, Israel.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of a halamishite specimen is assessed based on the quality of the entire rock sample in which it is found. The most desirable specimens are those where the presence of halamishite has been analytically confirmed (e.g., by an accompanying certificate with EDS analysis). The richness and aesthetics of associated minerals enhance its value, especially if they are well-formed. ## Popular localities The only source of halamishite specimens is the Hatrurim formation in Israel. Material from this locality is highly prized by collectors specializing in rare minerals, type locality minerals, and those formed by pyrometamorphic processes.

Care and storage

## Cleaning Specimens containing halamishite (typically rocks from the Hatrurim formation) should not be cleaned wet or chemically. Any contaminants should be removed exclusively with compressed air or a very soft brush to avoid damaging delicate associated minerals. ## What to avoid Avoid contact with water, acids, bases, and all chemical agents. Specimens should be protected from moisture, sudden temperature changes, and direct sunlight, which could affect the stability of associated minerals. ## Storage It is recommended to store specimens under stable conditions, preferably in sealed, dry containers (e.g., "membrane box" type boxes) or in cabinets with controlled humidity. This will protect microscopic crystals from dust, moisture, and mechanical damage.

Sources

IMA Mineral List (CNMNC)