IAB meteorites are a group of

iron meteorite Iron meteorites, also known as 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 i ...

s according to their overall composition and a group of

primitive achondrite Primitive achondrites are a subdivision of meteorites. They are classified on the same rank (historically called "Class") and lying between chondrites and achondrites. They are called primitive because they are achondrites that have retained much o ...

s because of silicate inclusions that show a strong affinity to

winonaite 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 c ...

s and

chondrite A chondrite is a stony (non- metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form pri ...

Description

The IAB meteorites are composed of

meteoric iron Meteoric iron, sometimes meteoritic iron, is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel, mainly in the form of the mineral phases kamacite and taenite. Meteoric i ...

(

kamacite Kamacite is an alloy of iron and nickel, which is found on Earth only in meteorites. According to the International Mineralogical Association (IMA) it is considered a proper nickel-rich variety of the mineral native iron. The proportion iron:ni ...

and

taenite Taenite is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with a chemical formula of and nickel proportions of 20% up to 65%. The name is derived from the Greek ταινία for "band, ribbon" ...

) and silicate inclusions. Structurally they can be

hexahedrite Hexahedrites are a structural class of iron meteorite. They are composed almost exclusively of the nickel–iron alloy kamacite and are lower in nickel content than the octahedrites. The nickel concentration in hexahedrites is always below 5.8% and ...

s, fine to coarse

octahedrites 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. Structure Oct ...

, or even

ataxite Ataxites (from Greek meaning "without structure") are a structural class of iron meteorites with a high nickel content and show no Widmanstätten patterns upon etching. Characteristics Ataxites are composed mainly of meteoric iron, a native metal ...

s. Most of them are

octahedrite 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. Structure Octahedr ...

with medium to coarse

-lamella and distinct

Widmanstätten pattern 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 ribbon ...

ing. The silicate inclusions are composed of low-Ca

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

, high-Ca

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...

troilite Troilite is a rare iron sulfide mineral with the simple formula of FeS. It is the iron-rich endmember of the pyrrhotite group. Pyrrhotite has the formula Fe(1-x)S (x = 0 to 0.2) which is iron deficient. As troilite lacks the iron deficiency whic ...

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

, different phosphates,

and traces of

daubréelite Daubréelite is a rare sulfide mineral. It crystallizes with cubic symmetry and has chemical composition of Fe2+Cr3+2S4. It usually occurs as black platy aggregates. Naming and history Daubréelite was named after the French mineralogist, petrol ...

and chromite. This composition is very similar to the composition of

s, and it is therefore argued that the two groups share the same parent body. There are also similarities with the IIICD meteorites, but it is not yet clear whether they are also part of that parent body.

Classification

The IAB group was created from the older IA and IB groups. Some authors also prefer to call it IAB complex. There are numerous subdivisions of the IAB group: *IAB main group *sLL subgroup *sLM subgroup (originally IIIC) *sLH subgroup (originally IIID) *sHL subgroup *sHH subgroup (includes Gay Gulch trio) *Udei Station grouplet *Pitts grouplet *Algarrabo duo *Mundrabilla duo *Britstown duo *NWA 468 duo *Twin City duo *solo irons related to IAB *IAB related?

Parent body

Most scientists believe that the

s and the IAB meteorites share the same parent body. It is not yet fully understood whether the IIICD meteorites also belong to that body.

Notable specimen

* Canyon Diablo *Pitts meteorite (part of Pitts grouplet) *Udei station meteorite (part of Udei station grouplet) *

Goose Lake Meteorite The Goose Lake meteorite is a meteorite that was found at Goose Lake in the United States by two hunters from Oakland, California on October 13, 1938. In 1939 it was acquired by the United States National Museum. From 1939 until January 14, 1941 ...

* Monturaqui *

Nantan meteorite The Nantan meteorite is an iron meteorite that belongs to the IAB group and the MG (main group) subgroup. In 2000, pieces of the meteorite were included in an art installation for The BullRing Shopping Centre in Birmingham, England. A plaque now ...

References

{{meteorites Achondrite meteorites

Description

Classification

Parent body

Notable specimen

See also

References