The achondrites of this group are named for a Greek philosopher
of the fifth century B.C., Diogenes of Apollonia. He was the first
to suggest that meteorites actually have their origin in outer space,
a fundamental realization that was subsequently forgotten for the
next two thousand years. The diogenites are as rare as an ingenious
spirit, and this group consists only of about 40 members if we
exclude all probable pairings, especially those that have been found
in the ice fields of Antarctica.
Mineralogically, the diogenites are composed primarily of
magnesium-rich orthopyroxene, with only minor amounts of olivine and
plagioclase. The pyroxenes are usually coarse-grained, suggesting a
cumulate origin for the diogenites in magma chambers within the
deeper regions of Vesta's crust. They are intrusive igneous rocks
similar to plutonic rocks found on Earth, and they experienced much
lower cooling rates than did the eucrites, which allowed the
pyroxene to form sizeable crystals. This is especially true for
Tatahouine, a unique diogenite that fell in Tunesia in 1931. This
meteorite is renowned for its green, centimeter-sized pyroxene
crystals. Other diogenites are monomict breccias, e.g. Bilanga, a
recent fall from Burkina Faso, Johnstown, a famous fall from
Colorado, USA, and Hamara, a most beautiful breccia from Morocco
recovered by our own team in April 2000. More recently, our team has
recovered another diogenite from Morocco, currently under
publication, that is a polymict fragmental breccia containing less
than 10% eucritic clasts. This analysis suggests that we have
discovered the first polymict diogenite - a true scientific
sensation.
Olivine Bearing Diogenite
(Jambon, Jussieu University 2003)
Provisional name LMT042
Find in 2001 in Occidental Sahara
TKW : 184 gr
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