Octahedrites are the most common structural class of iron meteorites. The structures occur because the meteoric iron has a certain nickel concentration that leads to the exsolution of kamacite out of taenite while cooling.
In meteoritics, a meteorite classification system attempts to group similar meteorites and allows scientists to communicate with a standardized terminology when discussing them. Meteorites are classified according to a variety of characteristics, especially mineralogical, petrological, chemical, and isotopic properties.
Widmanstätten patterns, also known as Thomson structures, are figures of long nickel–iron crystals, found in the octahedrite iron meteorites and some pallasites. They consist of a fine interleaving of kamacite and taenite bands or ribbons called lamellae. Commonly, in gaps between the lamellae, a fine-grained mixture of kamacite and taenite called plessite can be found. Widmanstätten patterns describe features in modern steels, titanium, and zirconium alloys.
Ataxites are a structural class of iron meteorites with a high nickel content and show no Widmanstätten patterns upon etching.
The pallasites are a class of stony–iron meteorite. They are relatively rare, and can be distinguished by the presence of large olivine crystal inclusions in the ferro-nickel matrix.
Iron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron meteorites originate from cores of planetesimals, with the exception of the IIE iron meteorite group
The iron meteorites of the IIE chemical type are octahedrites of various coarseness, most of which contain numerous inclusions of recrystallized stony silicates.
Mbozi is an ungrouped iron meteorite found in Tanzania. It is one of the world's largest meteorites, variously estimated as the fourth-largest to the eighth-largest, it is located near the city of Mbeya in Tanzania's southern highlands. The meteorite is 3 metres (9.8 ft) long, 1 metre high, and weighs an estimated 16 metric tons.
Primitive achondrites are a subdivision of meteorites. They are classified on the same rank and lying between chondrites and achondrites. They are called primitive because they are achondrites that have retained much of their original chondritic properties. Very characteristic are relic chondrules and chemical compositions close to the composition of chondrites. These observations are explained as melt residues, partial melting, or extensive recrystallization.
Lodranites are a small group of primitive achondrite meteorites that consists of meteoric iron and silicate minerals. Olivine and pyroxene make up most of the silicate minerals. Like all primitive achondrites lodranites share similarities with chondrites and achondrites.
Winonaites are a group of primitive achondrite meteorites. Like all primitive achondrites, winonaites share similarities with chondrites and achondrites. They show signs of metamorphism, partial melting, brecciation and relic chondrules. Their chemical and mineralogical composition lies between H and E chondrites.
IIICD meteorites are a group of primitive achondrites. They are classified in a clan together with the IAB meteorites and the winonaites.
IVB meteorites are a group of ataxite iron meteorites classified as achondrites. The IVB group has the most extreme chemical compositions of all iron meteorites, meaning that examples of the group are depleted in volatile elements and enriched in refractory elements compared to other iron meteorites.
The Vermillion meteorite is a pallasite (stony-iron) meteorite and one of two members of the pyroxene pallasite grouplet.
The pyroxene pallasite grouplet is a subdivision of the pallasite meteorites (stony-irons).
Stony-iron meteorites or siderolites are meteorites that consist of nearly equal parts of meteoric iron and silicates. This distinguishes them from the stony meteorites, that are mostly silicates, and the iron meteorites, that are mostly meteoric iron.
Nonmagmatic meteorite is a deprecated term formerly used in meteoritics to describe iron meteorites that were originally thought to have not formed by igneous processes, to differentiate them from the magmatic meteorites, produced by the crystallization of a metal melt. The concept behind this was developed in the 1970s, but it was quickly realized that igneous processes actually play a vital role in the formation of the so-called "nonmagmatic" meteorites. Today, the terms are still sometimes used, but usage is discouraged because of the ambiguous meanings of the terms magmatic and nonmagmatic. The meteorites that were described to be nonmagmatic are now understood to be the product of partial melting and impact events and are grouped with the primitive achondrites and the achondrites.
This is a glossary of terms used in meteoritics, the science of meteorites.
The Mundrabilla meteorite is an iron meteorite found in 1911 in Australia, one of the largest meteorites found, with a total known weight of 22 tonnes and the main mass accounting for 12.4 tonnes.
IIAB meteorites are a group of iron meteorites. Their structural classification ranges from hexahedrites to octahedrites. IIABs have the lowest concentration of nickel of all iron meteorite groups. Most iron meteorites are derived from the metallic planetary cores of their respective parent bodies, but in the case of the IIABs the metallic magma separated to form not only this meteorite group but also the IIG group.
