Farringtonite

Chemical formula: Mg₃(PO₄)₂

Farringtonite is an extremely rare magnesium phosphate, found mainly in meteorites, forming microscopic, colorless grains.

## Characteristics Farringtonite is a very rare mineral from the phosphate group, consisting mainly of magnesium phosphate. It occurs as very small, anhedral (irregularly shaped) grains or rounded aggregates, usually not exceeding a few hundred micrometers in size. Due to the microscopic size of its crystals, its visual characteristics are difficult to observe without specialized equipment. It is colorless and transparent. ## Physical Properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. It has a vitreous luster and is transparent. Its density, calculated based on the chemical formula and unit cell parameters, is approximately 2.81 g/cm³. It does not exhibit fluorescence under ultraviolet light. ## Colors and Varieties Farringtonite is typically colorless. No colored varieties or trade names are known, which is due to its extreme rarity and microscopic size. ## History and Name The mineral's name honors Oliver Cummings Farrington (1864–1933), a long-time curator of geology at the Field Museum of Natural History in Chicago, who was a distinguished specialist in meteorite research. The mineral was first described in 1961 based on a find in the Springwater pallasite meteorite, discovered in Canada in 1931. ## Uses Farringtonite has no industrial or commercial applications. Its significance is purely scientific and collectible, especially for specialists dealing with meteorites.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: White
Density: 2.81
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of farringtonite is possible only through advanced laboratory methods, such as electron microscopy with EDS analysis (energy-dispersive spectroscopy) or X-ray diffraction (XRD). In collecting conditions, it is unrecognizable due to its microscopic size and occurrence within other minerals. ## Distinguishing from Similar Minerals It can be confused with other phosphates found in meteorites, such as stanfieldite or graftonite. Differentiation requires precise chemical analysis – farringtonite is a pure magnesium phosphate, while other minerals additionally contain iron, calcium, or manganese. ## Crystal Forms It usually forms anhedral, rounded grains or small, irregular aggregates embedded in the meteorite matrix, often within olivine crystals or at the boundary between olivine and the metallic phase (kamacite/taenite).

Geological environment

## Genesis Farringtonite is an extraterrestrial mineral. It forms in stony-iron meteorites, mainly pallasites. Its genesis is linked to processes occurring within parent asteroids, where, under very low oxygen fugacity conditions, reactions took place between silicates (olivine) and primordial phosphorus. ## Mineral Associations This mineral co-occurs primarily with olivine and iron-nickel alloy (kamacite and taenite), which form the main mass of pallasites. It is also accompanied by other rare phosphates, such as stanfieldite, as well as schreibersite and troilite. ## Localities Confirmed occurrences of farringtonite are exclusively in meteorites. It has been identified, among others, in pallasites: Springwater (Saskatchewan, Canada – type locality), Brenham (Kansas, USA), Imilac (Atacama Desert, Chile), and Krasnoyarsk (Russia).

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a farringtonite specimen is practically identical to the quality of the meteorite in which it is found. For collectors and researchers, the confirmation of the mineral's presence through scientific analysis is paramount. Since farringtonite is invisible to the naked eye, its "visual appeal" is not a criterion for evaluation. The value lies in the mere fact of possessing a documented specimen of this extremely rare mineral. ## Popular Localities The most well-known specimens come from classic pallasite localities such as Springwater, Brenham, and Imilac. Fragments of these meteorites in which farringtonite has been identified are highly prized in specialized collections.

Care and storage

## Cleaning Specimens containing farringtonite, due to their nature (usually meteorite fragments), should not be cleaned with water. Any contaminants should be removed only with a soft brush or compressed air (with caution). ## What to Avoid Contact with water, chemicals, acids, and detergents should be absolutely avoided, as they can damage both the farringtonite itself and the surrounding meteorite material (mainly metallic). Pallasite meteorites are susceptible to rusting, so maintaining low humidity is crucial. ## Storage Specimens should be stored in a dry environment, preferably in an airtight container (membrane or plastic) with a desiccant (e.g., silica gel). They should be protected from dust and temperature changes.

Sources

IMA Mineral List (CNMNC)