Brachinites are a group of meteorites that are classified either as

primitive achondrites 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 ...

or as

asteroidal achondrites An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystalli ...

. Like all primitive achondrites, they have similarities with

chondrites A chondrite is a stony (non-Metallicity, metallic) meteorite that has not been modified, by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the ea ...

and

achondrites An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystalli ...

. Brachinites contain 74 to 98% (volume)

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 quickl ...

Naming and history

Brachinites are named after the

Brachina meteorite The Brachina meteorite is the type specimen of the brachinites class of the asteroidal achondrites. Naming and discovery The meteorite is named after Brachina in South Australia. Two fragments (total 200 g) were found by B.M. Eves at on 26 May ...

, the type specimen of this group, which in turn is named after Brachina,

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

Description

Brachinites consist almost entirely of

(74 to 98% by volume). Other minerals include

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 prope ...

(6.7 to 12.9%), iron sulfides (1.8 to 4.0%),

clinopyroxene 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) ...

(1.5 to 8.2%) and

orthopyroxene 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) ...

(0 to 2.4%). Trace minerals include phosphates and

meteoritic iron Meteoric iron, sometimes meteoritic iron, is a native metal and Primitive rock, 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 taenit ...

. The only deviation from

is the very high olivine/orthopyroxene ratio.

Specimens

As of 2022, there were 56 meteorites classified as brachinites. A notable example is the type specimen, the

References

{{meteorites Achondrite meteorites Asteroidal achondrites

Naming and history

Description

Specimens

See also

References