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NWA 5507   contributed by Cosimo Gorgoglione   MetBul Link

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TKW 2.5 kg. Fall not observed. Found 2008.

Cosimo writes:
The recommended classification L3 means:
An ordinary chondrite from the L group that is petrologic type 3.

The highlighted words are defined as follows:
ordinary chondrite: A major class of chondrites, distinguished by sub-solar Mg/Si and refractory/Si ratios, oxygen isotope compositions that plot above the terrestrial fractionation line, and a large volume percentage of chondrules, with only 10-15 vol% fine-grained matrix.

L group: The low-iron (L) chemical group of ordinary chondrites, distinguished by their relatively low siderophile element content, moderate sized chondrules (~0.7 mm), and oxygen isotope compositions that intermediate between H and LL group ordinary chondrites.

type 3: Designates chondrites that are characterized by abundant chondrules, low degrees of aqueous alteration, and unequilibrated mineral assemblages. Many of the low-Ca pyroxene grains are monoclinic and exhibit polysynthetic twinning. The type 3 chondrites may be divided into subtypes ranging from 3.00 (least metamorphosed) to 3.9 (nearly metamorphosed to type 4 levels). If primary igneous glass occurs in the chondrules, it belongs to type 3.

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Aguas Zarcas
Mike Farmer

This Month

 8/9/2019 5:23:31 PM
Fresh type 3's like this are inspirational, thanks Cosimo
Zelimir Gabelica
 8/9/2019 10:33:08 AM
NWA 5507, found in 2008, was only officially classified in February 2017. Marcin Cimala claimed at the time (2008) it being of L3.2 type and this was valid for 9 years...The new official classification now proposes L3. In regard of the detailed composition and texture (not reported inMetBull), does somebody know which type is now the most likely ? Your thoughts Marcin ?, Bernd ?
Bernd Pauli
 8/9/2019 9:06:32 AM
My two NWA 5507 slices have abundant finely crystalline troilite and several troilite-rimmed chondrules.

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