Those meteorites are fragments of "non-differentiated
parent bodies". They have not been modified since creation
of the solar system and thanks to isotopic analyses carried out
on those meteorites, scientists have been able to measure the
age of the solar system (and of the Earth as well), as 4.5 billion
years.
The name "Chondrite" comes from the name
of the small spheres that they contain, the chondrules, that can
never be found in the structure of any terrestrial stone.
CHONDRULES DISPLAYED
ON THE POLISHED SECTION OF A CARBONACEOUS CHONDRITE
There are several groups of chondrites:
- Ordinary chondrites (H, L,
LL groups):
They are the most common meteorites (80 % of the total
known meteorites).
They contain "free iron" (non oxidized) and are classified
according to their iron content:
H Type
(High) : between 12 and 21% iron
L Type (Low) : between
7 and 12% iron
LL Type (Low-Low) : less
than 7% iron
An additional information about metamorphism is provided
by a figure (between 3 and 7)
example : an L3 chondrite is slightly metamorphised and contains
between 7 and 12% of Fe-Ni.
- Enstatite chondrites (EL and
EH groups):
They are rare and their iron
content is higher: up to 35% for EH.
- Carbonaceous chondrites (CI,
CM, CO, CV, CK, CR... groups):
Those meteorites are also rare and are the most primitive
ones. Their composition is very close to the one of the proto-solar
cloud that origintated the solar system.
They contain carbon and low amount of iron, mostly
under oxidized form.
(TANEZROUFT 057 - C4 an)
(ADRAR BOUS - EL5)
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