Barringerite
Chemical formula: (Fe,Ni)<sub>2</sub>P
A very rare iron-nickel phosphide, occurring as microscopic grains in iron meteorites.
Description
## Characteristics Barringerite is a mineral with a metallic luster and opaque nature. It occurs as extremely small, irregular grains or thin lamellae, usually not exceeding a few tens of micrometers in size. For this reason, its observation requires the use of a petrographic microscope or a scanning electron microscope. Typical specimens are actually polished fragments of meteorites in which this mineral has been identified. ## Physical Properties This mineral is characterized by high hardness, ranging from 6.5-7 on the Mohs scale. It has a metallic luster and is completely opaque. Its density, calculated based on chemical composition and crystal structure, is approximately 7.1 g/cm³, however, direct measurement is impossible due to the microscopic size of the grains. ## Colors and Varieties Barringerite is tin-white to cream-white in color. Due to its rarity and specific occurrence conditions, no color varieties or commercial forms are distinguished. ## History and Name The mineral was described in 1969 by P. S. Buseck. The name honors Daniel Moreau Barringer (1860-1929), an American mining engineer who first presented evidence for the meteoritic origin of the Barringer Crater in Arizona. The type locality for this mineral is the Canyon Diablo meteorite, fragments of which are found around this crater. ## Applications Barringerite has no industrial applications. Its significance is purely scientific, providing information about processes occurring within the parent bodies of asteroids from which iron meteorites originate.
Diagnostic features
## Identification Identification of barringerite with the naked eye or a magnifying glass is impossible. Recognition requires advanced laboratory techniques, such as scanning electron microscopy with chemical composition analysis (SEM-EDS) or X-ray diffraction (XRD). A preliminary indication is its occurrence in association with other meteoritic minerals. ## Distinguishing from Similar Minerals Barringerite is most often confused with schreibersite ((Fe,Ni)₃P), which is a much more common phosphide in meteorites. Visual differentiation is impossible. They differ in the ratio of metal atoms to phosphorus (2:1 for barringerite, 3:1 for schreibersite) and crystallographic system (hexagonal for barringerite, tetragonal for schreibersite). It can also be confused with other metallic phases, such as troilite (FeS) or cohenite (Fe₃C). ## Crystal Forms This mineral does not form well-developed crystals. It occurs as anhedral (irregular) grains or thin, elongated lamellae intergrown with other minerals, most commonly troilite.
Geological environment
## Genesis Barringerite is an extraterrestrial mineral. It forms as a result of very slow cooling of an iron-nickel melt in the cores of asteroids, which are the parent bodies for iron meteorites. It crystallizes under conditions of high temperature and extremely low pressure (cosmic vacuum) as one of the later mineral phases. ## Mineral Associations This mineral co-occurs with other components of iron meteorites. Its most common companions are kamacite and taenite (main Fe-Ni alloys), schreibersite, troilite, and cohenite. ## Localities The Canyon Diablo meteorite, found near Barringer Crater in Arizona, USA, is given as the type locality. Its presence has also been confirmed in other iron meteorites, for example, in the Udei Station meteorite (IAB group).
Rarity
Very rare
Collector aspects
## Quality Criteria In the case of barringerite, the quality of the specimen is not discussed in the traditional sense. It is a microscopic mineral, so its collector value as a separate object is zero. However, the meteorite specimen itself, in which the presence of this rare mineral has been confirmed, has value. For specialized scientific or university collections, a polished thin section of a meteorite with a precisely located and documented barringerite grain is a valuable acquisition. ## Popular Localities The only source of barringerite is iron meteorites. The most classic and well-known material in which it has been identified are fragments of the Canyon Diablo meteorite from Arizona.
Care and storage
## Cleaning Cleaning individual barringerite grains is not practical. The specimen, which is a meteorite fragment containing the mineral, should only be dry-cleaned using a soft brush to remove dust. Any contact with water and chemical agents should be avoided. ## What to Avoid The greatest threat to barringerite, as well as to the entire iron meteorite, is moisture. It causes rapid oxidation (rusting) of the metallic phases. Storage in damp rooms, sudden temperature changes, and direct contact with skin, which transfers moisture and salts, should be avoided. ## Storage Meteorite specimens containing barringerite should be stored in the driest possible conditions. It is recommended to use sealed plastic containers (e.g., membrane boxes) along with a desiccant (e.g., silica gel).