chondrite

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chondrite Stony meteorite; the majority of chondrites are characterized by the presence of chondrules, and they constitute about 86% of meteorite falls. The principal minerals they contain are olivine, pyroxene, plagioclase feldspar, troilite, and the iron-nickel minerals kamacite and taenite. Chondrites are grouped according to their petrological type (texture, crystal structure, etc.) into six classes. On the basis of their chemical composition they fall into five main groups: enstatite chondrites (highly reduced, iron in metallic form); high-Fe (H) chondrites; low-Fe (L) chondrites; low-Fe/low-metal (LL) chondrites (some iron in silicate form); and carbonaceous chondrites (relatively high oxidation levels, containing volatiles). C1 chondrites are often used as a chemical model for the bulk composition of the Earth, but there are notable discrepancies, e.g. in the proportions of volatile elements.

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Chondrites With Zoophycus, an ichnoguild of many-branched, radial, trace fossils probably made by a worm that moved back and forth through the sediment, each branch of its burrow exploring a new area.

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chondrite model (chondritic Earth model) Hypothesis that the bulk composition of the Earth is close to that of carbonaceous chondrites.

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chondrite: see meteorite.