OSM 012 (CO3)
Classification led by Cesca Willcocks
This meteorite belongs to Sean Mahoney & Gemma Thomas, and was found as a single stone in Northern Algeria in April 2020.
This meteorite will possibly receive an official name of 'Erg Chech ***' - to be confirmed by the Nomenclature Committee of the Meteoritical Society.
The type specimen (20.73 g) will be on deposit at the University of Plymouth, along with a single, polished thin section.
Backscatter Electron (BSE) imagery is useful for looking at the distribution of elements across a sample based on their atomic number (where the brighter phases are of higher density). As well as this, BSE imagery can help us pinpoint textures exhibited by a sample, and in OSM 012 was particularly useful in identifying where chondrules were present.
We found that OSM 012 had an abundance of chondrules (both barred and porphyritic) that had an average diameter of 321.5 microns (n = 35). Not only were lots of chondrules present, but the sample was also relatively pristine with very small (as small as 65 microns), well rounded chondrules also preserved.
BSE image of OSM 012 used to observe chondrules across the sample. An example of a porphyritic chondrule can be seen in the yellow box.
Combined element map for OSM 012 where red = olivine, dark blue = Fe phases, teal = plagioclase, light blue = CAIs
Energy Dispersive Spectroscopy (EDS) allows us to look at the chemical composition of a sample by mapping where each element is present across the sample surface. EDS can produce element maps for individual elements across the sample. Combining these maps together, allocating a colour to each element and normalising them by stoichiometry can help us pick out which minerals are present and where compositionally different features appear. This was a useful tool during the classification of OSM 012 as we were able to identify where Calcium-Aluminium Inclusions (CAIs) and Amoeboid Olivine Aggregates (AOAs) - two features present in Carbonaceous Chondrites - were present across the sample. From these maps we were also able to decipher the minerals present within the chondrules observed in the BSE image above.
OSM 012 had an abundance of CAIs and AOAs as well as olivine fragments, plagioclase, Fe-rich phases, and a fine grained phyllosilicate groundmass.
Sean is a meteorite collector and dealer based in Spain, and a registered member of both the IMCA and GMA.
You can find out more about Sean's meteorite collection, OuterSpacer Meteorites, on his web page.
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