NWA 11359 8.5g, a very abnormal L6 S2 W1 specimen, full slice

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Description

One of the old adages about identifying meteoritic vs. terrestrial specimens says the following “Meteorites are not porous.” More often than not that is true. Usually a rock that looks like it has a bunch of holes in it is a volcanic rock, and more often than not those are black (like most meteorites) so it is a useful rule in general.

 

However, for every rule there is an exception, and NWA 11359 is one of those exceptions. The classification itself is an L6, undoubtedly the most common of the ordinary chondrites, but without a doubt 11359 is unique among them. Amidst Dr. Alan Rubin’s classification he states the “The stone is unusually porous. It contains 5-10 vol.% pores with diameters ranging from 50 – 250 µm” and boy is that ever obvious once you cut it. The space between chondrules is abundant at first glance, and the gestalt of the cut surface is something like of a network of chondrules holding hands, all struggling to maintain their grip on each other.

 

But, the unique qualities of NWA 11359 do not stop there. While most all meteorites contain some degree of recrystallization, and this is true of the L6 class in general, 11359 stands out in the crowd in this regard as well. Again, to refer to Dr. Rubin’s classification, “The stone is very recrystallized…” with further note being made to increased amounts of plagioclase grains and diopside. When you examine the specimens as a whole, they look to have much more of a mineral and/or gem-like quality than the average L6 for these reasons.

 

Most of my specimens I polish as close as I can get them to 3000 grit. It’s a tedious process because sanding belts at 3000 grit don’t seem to exist, so polishing them by hand is the only option. It is tedious, and often painful on the fingers. When I first started preparing specimens of 11359, I felt that the recrystallized nature of the meteorite would result in a very attractive cut surface when it was polished 3000. That was a mistake. The small specks of dust produced by the polishing process fit very well inside the porous openings between chondrules, and as a result the entire cut surface starts to obscure the appreciation of the chondrules. Like most L6 specimens, NWA 111359 looks best at a low grit polish, so these cut surfaces have been left at 125 grit for that reason.

 

The criteria that make a specimen anomalous does not encompass features like porosity and recrystallization. While the classification of 11359 may only be an L6, it is truly a rare classification overall due to the many features of the specimen that are otherwise never seen in this very common classification.

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