Galileiite

Chemical formula: NaFe₂+₄(PO₄)₃

Galileite is a very rare, dark green to black phosphate mineral, found exclusively in meteorites.

## Characteristics Galileite is a very rare sodium iron phosphate, occurring as small, rounded grains up to 200 micrometers in size. It typically forms aggregates with other phosphate minerals. Its color ranges from dark green to almost black, and in transmitted light, it reveals an intensely green color without pleochroism. ## Physical Properties This mineral is characterized by a vitreous luster and is opaque, although very thin fragments can be translucent. It has a hardness of approximately 5 on the Mohs scale and a density of 3.86 g/cm³. It exhibits no cleavage, and its fracture is uneven. ## History and Name Galileite was first described in 1997 by A. M. Fioretti, G. Molin, M. Mellini, A. C. Corrêa-Neves, and S. A. S. de Almeida. Its name honors Galileo Galilei (1564-1642), an Italian astronomer and physicist, in recognition of his contributions to science. The mineral was approved by the International Mineralogical Association (IMA) under number IMA1995-037. ## Uses Due to its extreme rarity and occurrence exclusively as microscopic grains in meteorites, galileite is of scientific and collector's interest only (in the form of micromounts).

Properties

Mohs hardness: 5
Luster: Vitreous
Density: 3.86
Cleavage: None
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of galileite is possible only through advanced laboratory methods, such as chemical analysis (electron microprobe) and X-ray diffraction (XRD), due to its microscopic size and occurrence in complex assemblages. In reflected light, it has a gray color with a greenish tint and weak bireflectance. ## Distinguishing from similar minerals It can be confused with other phosphates found in meteorites, such as johnsomervilleite, sarcopside, or graftonite. Differentiation requires precise chemical analysis – galileite is distinguished by its specific sodium and iron stoichiometry. ## Crystal forms Galileite occurs as anhedral (lacking crystal faces), rounded grains, typically 50 to 200 micrometers in diameter. It forms simple intergrowths with other phosphates.

Geological environment

## Genesis Galileite is a mineral of extraterrestrial origin. It forms in iron meteorites (siderites), specifically in IAB-type octahedrites. It crystallizes in silicate nodules within the metallic matrix (kamacite and taenite) as a result of the crystallization of a phosphate melt during the cooling of the parent celestial body. ## Mineral associations This mineral coexists with other phosphates, such as sarcopside, graftonite, and johnsomervilleite. It is also accompanied by chromite, troilite, graphite, diopside, orthopyroxene, and metallic iron-nickel phases (kamacite, taenite). ## Localities The only confirmed locality for galileite is the Angra dos Reis iron meteorite, which fell in 1869 in the state of Rio de Janeiro, Brazil. This is the type locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of a galileite specimen is determined by the quality of the meteorite fragment in which it is found. For scientific and collecting purposes (micromounts), the most important factors are the unambiguous identification of the mineral in a polished section and the richness of the mineral association. The size of galileite grains is also a significant factor. ## Popular localities The only source of specimens is the Angra dos Reis meteorite from Brazil. Fragments of this meteorite are extremely rare and are mainly found in institutional and museum collections.

Care and storage

## Cleaning Specimens containing galileite, being meteorite fragments, should generally not be wet cleaned. Dust can be removed very carefully with a soft brush or compressed air from a safe distance. ## What to avoid Avoid contact with water, chemicals, and ultrasonics. As a component of iron meteorites, it can be susceptible to oxidation in humid environments. It should be protected from moisture and sudden temperature changes. ## Storage Storage in stable conditions is recommended, preferably in a sealed container with a desiccant (e.g., silica gel). Display should be in a dry place, away from direct sunlight.

Sources

IMA Mineral List (CNMNC)