An Article In Meteorite-Times Magazine
by Robert Verish
An Article In Meteorite-Times Magazine
by Robert Verish
Sand Encrusted Stones of the NWA 869 Meteorite
Sand grains from the Sahara Desert are caliche-cemented to the exterior of unwashed chondritic stones of the NWA 869 meteorite.
For the purpose of this article, any NWA meteorite that is encrusted with caliche-cemented sand-grains would have sufficed, but the NWA 869 meteorite is best suited for a study of this kind for these reasons:
There are at least 2 metric tons of this meteorite comprising thousands of individuals.
Individual masses are known to range from <1 g to >20 kg, with the majority of stones being less than 1kg.
The vast majority of these stones have a uniform, yet, distinctive appearance.
Many specimens are readily available and are comparatively cheap.
And if the strewn field that these stones come from is not too vast, it is hoped that the encrusted sediment is uniform in composition.
The "hoped for" payoff coming from a study focusing on clay and sand-grains is that a "finger-print" will emerge from a uniform, yet distinctive, desert sediment. One that could used as a diagnostic tool.
The good news is - this desert sediment does look uniform in composition and morphology.
"Click" on the above image of the NWA 869 (L4-6) Meteorite for a Close-Up view!!
The image at the top of this page depicts the four stones used in this image gallery. For a sense of scale, the specimen was placed next to a 1 cm cube scale. Note in the lower image that the 1 cm cube has been turned over and now displays the "B"-side (for Bottom-side). This denotes that this is the bottom-side of this find; the side that was down and in contact with the ground when it was found.
In the images below, the meteorite has been magnified with a hand lens. In these images the field of view is approximately 2 centimeters wide.
"Click" on the above image of the NWA 869 (L4-6) Meteorite for an ENLARGED view!!
In the image below, the same patch of encrusted sand but through the eyepiece of a microscope (x10).
"Click" on the above image of the NWA 869 (L4-6) Meteorite for an ENLARGED view!!
In the view below, it is the same image, but it has been ENLARGED.
"Click" on the above image of the NWA 869 (L4-6) Meteorite for an ENLARGED view!!
The 3 images below depict the other 3 stones.
"Click" on the above images of the sand encrusted NWA 869 (L4-6) Meteorite stones for an ENLARGED view!!
Here is another view of the 2nd stone (the stone 2nd from the left in the first image).
"Click" on the above image of the NWA 869 (L4-6) Meteorite for an ENLARGED view!!
An here are two more images of patches of encrusted sand from the other two stones, taken through the eyepiece of a microscope (x10).
"Click" on the above image of the NWA 869 (L4-6) Meteorite for an ENLARGED view!!
This ends the image gallery for these four specimens of NWA 869. In the future more images (of other specimens) may be added here. But for now, these four specimen provide sufficient evidence that the encrustation originates from a desert soil of uniform, yet distinctive, composition and sand-grain morphology. In addition, when compared to encrusted sand-grains on my specimen of the Bouse (L4-6) Meteorite, there is very little similarity (see my image gallery for the 15gram Bouse (L4-6) Stone. More of this kind of detailed examination is needed before any assumption can be made that these two meteorites are possibly paired.
UPDATE:
After I published this article, I discovered the real reason why there was "very little similarity" between my "15gram Bouse (L4-6) Stone" and the four specimens of NWA 869 (pictured in the above article). There was something wrong with my Bouse specimen.
It had been stated by the finder and the classifier that the "3 original stones" of the Bouse meteorite "had never been cleaned", but upon closer examination of my specimen, it was evident that this wasn't the case.
Whether the exterior of my "Bouse" meteorite with the residual sand-grains in the cracks is the result of natural weathering, or scrubbing (by human hands), may never be resolved, but in any case, this was the "last straw" in a series of red-flags that have been raised concerning the provenance of the "Bouse" finds. Comparing the exterior of this "Bouse" specimen with one of my "dirty" NWA 869 that was "scrubbed", and with other NWA 869 specimens that were advertized as being "cleaned by the dealer prior to their sale", showed VERY LITTLE DIFFERENCE in gross appearance, as well as residual quartz-grain morphology.
A proper scientific study of the sand-grains still needs to be conducted. But, there is little interest, now, in conducting such an analysis, if it is only going to prove that the sand-grains on the Bouse and NWA 869 meteorites are "paired".
(That's not to say that this wouldn't be a valid scientific inquiry. It's just that it would be a forensic study, and not really a meteorite study. And considering the "negativity" that would result from a "proved pairing", it appears that the general consensus is that the less said, the better.)
And that's where this study still stands at this time.
REFERENCES:
My prior Bob's Findings articles on the Bouse Meteorite:
| August 2007 |
The Bouse Meteorite
Image Gallery of the original 15.7 gram stone |
| September 2007 |
The Bouse Meteorite - Part 2
Is there any evidence that Bouse (L4-6) is paired to NWA 968 (L4-6)?? |
Published papers of other studies:
Sand grains were examined for use in confirming recovery location of the Twannberg meteorites:
[PDF] 69th Annual Meteoritical Society Meeting (2006) 5128.pdf
| File Format: PDF/Adobe Acrobat - View as HTML
silicate sand grains, identical to those occurring in local glacial ... Discussion: Twannberg is a large meteorite with an unusually young CRE age. ... |
Quartz sand grains in the red desert soils of Northwest Africa:
Morphology and mineralogy of red desert soils in the Libyan Sahara Desert
| The sand grains are again dominantly quartz, with. traces of weathered feldspar and rock fragments. The quartz grain types are similar to those of the ... |
Quartz sand grain morphology - an early reference document:
[PDF]Some Observations on Electron Micrographs of Quartz Sand Grains
| File Format: PDF/Adobe Acrobat - View as HTML "striations", and in sand-grain morphology some abrasion marks attributed to aeolian abrasion are similarly named. One has to determine from the context which ... |
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