The H type ordinary chondrites are the most common type of

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

, accounting for approximately 40% of all those catalogued, 46% of the ordinary chondrites, and 44% of all

chondrite A chondrite is a stony (non-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 early Solar Syste ...

s. The ordinary chondrites are thought to have originated from three parent asteroids, whose fragments make up the H chondrite, L chondrite and

LL chondrite LL may refer to: * Ll or ll, a digraph that occurs in several natural languages Arts and entertainment *LL, the production code for the 1967 ''Doctor Who'' serial ''The Evil of the Daleks'' * ''Labyrinth Lord'', a fantasy role-playing game * ''L ...

groups respectively.

Name

The name comes from their High iron abundance, with respect to other ordinary chondrites. Historically, the H chondrites have been named ''bronzite chondrites'' or ''olivine bronzite chondrites'' for the dominant minerals, but these terms are now obsolete.

Parent body

A probable parent body for this group is the S-type asteroid 6 Hebe, with less likely candidates being 3 Juno and 7 Iris.M. J. Gaffey & S. L. Gilbert ''Asteroid 6 Hebe: The probable parent body of the H-Type ordinary chondrites and the IIE iron meteorites''
Meteoritics & Planetary Science, Vol. 33, p. 1281 (1998). It is supposed that these meteorites arise from impacts onto small near-Earth asteroids broken off from 6 Hebe in the past, rather than originating from 6 Hebe directly. The H chondrites have very similar trace element abundances and

Oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

isotope ratios to the IIE iron meteorites, making it likely that they both originate from the same parent body.

Iron

Their high iron abundance is about 25–31% by weight. Over half of this is present in metallic form, making these meteorites strongly magnetic despite the stony chondritic appearance.

Mineralogy

The most abundant minerals are bronzite (an orthopyroxene), and

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

. Characteristic is the

fayalite Fayalite (, commonly abbreviated to Fa) is the iron-rich endmember, end-member of the olivine solid solution, solid-solution series. In common with all minerals in the olivine, olivine group, fayalite crystallizes in the orthorhombic system (spac ...

(Fa) content of the olivine of 16 to 20 mol%. They contain also 15–19% of nickel-iron metal and about 5% of troilite. The majority of these meteorites have been significantly metamorphosed, with over 40% being in petrologic class 5, most of the rest in classes 4 and 6. Only a few (about 2.5%) are of the largely unaltered petrologic class 3.

Gallery

File:GaoGuenieMeteorite.jpg, Gao-Guenie, H5 File:Chondrite H5.JPG, H5 Dar Bou Nali South Morocco

References

External links

The Catalogue of Meteorites
{{DEFAULTSORT:H Chondrite fi:H-kondriitti