New England
Meteoritical Services
Ordinary Chondrites
Ordinary
chondrites are the most common type of
stone meteorite, if "ordinary" and "common" are terms that can be applied to
objects that have survived billions of years in outer space and a fiery plunge
through our atmosphere at velocities measured in tens of kilometers per
second.
Ordinary chondrites are further
grouped by H, L and LL classifications, indicating iron content, and by the
numbers 3-7, indicating the amount of change or metamorphism in the
chondrules.
H chondrites have the highest
iron content - 27 percent total iron by weight. They are commonly referred to
as olivine-bronzite chondrites. L
chondrites have a lower iron content, roughly 23 percent by weight and are
referred to as olivine-hypersthene chondrites. LL
chondrites represent "low iron" and "low metal" content. Sometimes referred to
as amphoterites, they contain only 20 percent total iron.
The numbers following the H, L
and LL classifications are petrologic
grades indicating the degree of chondrule alteration by heating. Well defined,
unaltered chondrules have a petrologic grade of 3 or 4. A higher number of 5 or
6 indicates an increased level of metamorphism making the chondrules less
distinct.
Combining naming and
classification conventions results in a specific specimen identification, such
as the Saratov L4 olivine-hypersthene
chondrite (13K GIF) from our Photo Gallery.

New England
Meteoritical Services
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