N'Goureyma
The N'Goureyma meteorite has a recorded fall
date of June 15th, 1900 and was said to have fallen near Djenne, Ke Macina, Mali in
Africa. It was a remarkably oriented specimen weighing 37.5kg
which was reportedly recovered from a hole 1m deep in clay. The
single mass was acquired by H. Minod (from Comptoir
Minéralogique et Géologique, Geneva), who cut and distributed it
from 1900 and in the following years at a price of 2-3 Francs
per gram. An old photomicrograph (Cohen, 1901a) is pictured
below and details the original amazing shape of this meteorite.
N'Goureyma has been classified as an
Anomalous Ungrouped Iron. Specifically it is an anomalous,
polycrystalline
(composed of aggregates of crystals; "polycrystalline metals"),
troilite rich iron with a martensitic-plessitic matrix. There is
an absence of a Widmanstätten structure and an obvious fine
distribution of troilite. This is highly evident in the
photographs below as the very unusual and uniquely shaped
inclusions. Renowned iron meteoriticist, Vahn Buchwald, has said
that N'Goureyma may be the result of aggregation plus sintering
of fine-grained material, followed by a cooling that was
relatively rapid compared to what the normal octahedrites
underwent. He also said that the metallic part of N'Goureyma
resembles in numerous respects the metal of Tucson (Ring) and
the polycrystalline structure may be the result of sintering at
1000-1200°C, where sulphur-rich liquids promoted the
densification.
Very little of N'Goureyma has made it into
private collections and it is likely the specimen below was
originally from a US Institution before heading back to Europe
and finally becoming part of the Meteorites Australia Collection (MA.05.0117).
The reverse side has heavy saw marks which, given its obvious
old oxidated surface, may very well represent one of the
original samples removed around the fall date.
![N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice](http://www.meteorites.com.au/collection/N'Goureyma%20ANOM-UNGR%203.7g%20(1%20of%204).jpg)
N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice.
(Click image to enlarge in new window.)
![N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice](http://www.meteorites.com.au/collection/N'Goureyma%20ANOM-UNGR%203.7g%20(2%20of%204).jpg)
N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice.
![N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice](http://www.meteorites.com.au/collection/N'Goureyma%20ANOM-UNGR%203.7g%20(3%20of%204).jpg)
N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice.
(Click image to enlarge in new window.)
![N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice](http://www.meteorites.com.au/collection/N'Goureyma%20ANOM-UNGR%203.7g%20(4%20of%204).jpg)
N'Goureyma (Ungrouped Anomalous Iron) - 3.7g Partslice.
(Click image to enlarge in new window.)
![N'Goureyma Meteorite](http://www.meteorites.com.au/images/N'Goureyma%20Litho.jpg)
N'Goureyma (Ungrouped Anomalous Iron)
(Scan courtesy: Dr. Svend Buhl.)
Click here to view the archive of the Monthly Favourites
|