Muonionalustaite

Chemical formula: Ni₂+₃(OH)₄Cl₂·₄H₂O

Muonionalustaite is an extremely rare, secondary nickel mineral, discovered as a weathering product in the Muonionalusta iron meteorite.

## Characteristics Muonionalustaite is a hydrated nickel hydroxychloride, forming microscopic, transparent crystals. It typically occurs as small, rosette-like aggregates or thin coatings on the meteorite surface. The crystals are in the form of thin, hexagonal plates and reach sizes up to about 0.2 mm. Due to its chemical composition, this mineral has a characteristic, vivid, blue-green or emerald-green color. ## Physical Properties The mineral is very soft, with a hardness of about 2 on the Mohs scale. Its luster is described as vitreous, and pearly on cleavage surfaces. It is transparent, and its density, calculated based on composition and structure, is 2.73 g/cm³. It is brittle and exhibits perfect cleavage in one direction. ## Colors and Varieties The dominant and only known color of muonionalustaite is an intense green in shades from emerald to blue-green. No varieties have been distinguished. ## History and Name The mineral was approved by the International Mineralogical Association (IMA) in 2009, and its description was published in 2010. The name comes from the Muonionalusta meteorite, in which it was first identified. This meteorite, an iron octahedrite, was found in 1906 in the municipality of Pajala in the Norrbotten region of Sweden, near the border with Finland. ## Applications Muonionalustaite has no industrial applications. Its significance is purely scientific and collectible, as a unique weathering product of extraterrestrial matter under terrestrial conditions.

Properties

Mohs hardness: 2
Luster: Vitreous, Pearly
Streak: Pale green
Density: 2.73
Cleavage: Perfect on {010}
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification The key diagnostic feature of muonionalustaite is its unique occurrence – exclusively as a weathering product on the Muonionalusta iron meteorite. Its vivid, blue-green color, platy crystal habit, and co-occurrence with other secondary minerals on the meteorite are also important clues. However, definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other secondary, green nickel minerals that can form on meteorites, such as zaratite or reevesite. However, zaratite is amorphous and has a reniform or botryoidal habit, while reevesite crystallizes in the trigonal system. In practice, without specialized equipment, differentiation is impossible, and the main criterion remains confirmed origin from the Muonionalusta meteorite. ## Crystal Forms It forms thin, hexagonal in outline, platy crystals. Most often, they occur as radial or rosette-like aggregates, as well as small, scattered flakes on the matrix surface.

Geological environment

## Genesis Muonionalustaite is a secondary mineral. It forms as a result of the weathering of primary, nickel-rich minerals of the iron meteorite (mainly kamacite and taenite) under the influence of the Earth's atmosphere and groundwater containing chloride ions. This process occurs after the meteorite has fallen to Earth. ## Mineral Associations This mineral co-occurs with primary meteorite components such as kamacite, taenite, and schreibersite. It is also accompanied by other weathering products, including goethite, akaganéite, hibbingite, and magnetite. ## Localities The only known locality (type locality) of this mineral in the world is fragments of the Muonionalusta meteorite, found in the Norrbotten region of northern Sweden.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, specimens with well-formed, sharp crystals forming rich, rosette-like aggregates are most highly valued. The intensity and attractiveness of the blue-green color also enhance visual appeal. Contrast with the meteoritic matrix and minimal damage to the delicate crystals are also important. ## Popular Localities The only specimens come from the Muonionalusta meteorite found in Sweden. Fragments of this meteorite with visible concentrations of muonionalustaite are extremely rare and are a target for specialized mineral and meteorite collectors.

Care and storage

## Cleaning Specimens should only be dry-cleaned, using a soft brush or a gentle stream of compressed air to remove dust. Any contact with water and other liquids should be avoided, as they can dissolve or damage this delicate mineral. ## What to Avoid Water, chemical solutions, ultrasonic cleaners, and sudden temperature changes must be strictly avoided. As a hydrated mineral, it can dehydrate in dry air or under heat, leading to its destruction. It is very soft and brittle, making it extremely susceptible to mechanical damage. ## Storage It is recommended to store specimens in closed, stable containers, such as "micromount" boxes, in an environment with controlled, low humidity. Consider using desiccants (silica gel) near the specimen to prevent its degradation.

Sources

IMA Mineral List (CNMNC)