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Tom Phillips Micrographic
NWA 5000 (Lunar Highlands)
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This gallery shows the NWA 5000 (Lunar Highlands) Thin Section in Cross Polarized Light. Adam Hupe purchased the stone in Morocco
and brought a sample to Dr. Tony Irving of University of Washington for examination and classification. This was the first thin section
made of this material. Dr. Irving was working with the thin but it was between examinations so he sent it to me, at Adam's request.
What a pleasure it was examining this material and to be able to discuss what I was looking at with Dr. Irving.
My forte is meteorite micrographic art. It’s a little science, but mostly it’s visually pleasing so I was quite jazzed to be “in the loop” in
any way I could. The first thing I noticed was the glass. Dr. Irving informed me that technically, this glass (plagioclase) is not a solid but
a super cooled liquid, and that the glass in NWA 5000 probably was produced by ancient impacts into the dominant gabbroic rock on the
Moon long before the final impact ejection of this meteorite. In this glass were lots of tiny bubbles. I showed my shots to Dr. Irving and
he said these bubbles are called vesicles, and they are the result of solar wind, trapped in glass. How cool!!!
Classification information from The Meteoritical Bulletin can be found here:
The very cool solar wind Vesicles are found in the glass, and the trouble with this glass is it is nearly completely isotropic. What that
means is, when you use cross polarized light, the glass is black and these black dots (Vesicles) against a black background are hidden.
So in standard full Xpol, they would be easy to miss.
Please keep in mind, I usually share only the most beautiful images but this material is so interesting and important I am also sharing
many less attractive shots that I found to show unusual features. For example, these shots were taken of the thin section viewed in
incident (reflected) light at a magnification of 345X:
Just for fun I took a few shots in DIC (Differential Interference Contrast). No great discovery here but still cool!
160X solar wind vesicles. This is the magnification level where I start to get "dialed in". Technique is the same as above.
Finally I take it up to 760X utilizing the same techniques as the 400X set.
Additionally, These two images are of a polished thick sample. It was polished to a level of 1/4 micron and viewed in incident light at a
magnification of 700X. The images were taken on an aus Jena Neophot microscope.
OK, now that I have shown what the vesicles look like in reflected light, lets see some Xpol. I start out at 85X. As I was viewing the
vesicles I saw so many beautiful sights . Various mineral grains and features born out of melted material cooling from a liquid. This is
not in my preferred magnification range but it gives a nice perspective of size. Look how the glass appears to be a river current frozen
This set was taken at a magnification of 400X in transmitted (pass through) cross polarized light. These shots utilized a PlayStation 3
Quarter Wave Plate. I tore apart a PS3 disk reader assembly just to see what I could do with the wave plate (retardation filter). It
worked out great!
It was difficult to show the vesicles nicely with out having the glass matrix as an intense color that would drown out the image. I set the
polarizer to about 45 degree off extinction and the quarter wave plate to just a nudge off of full extinction. This allowed me to draw out
color from mineral grains while keeping the glass relatively neutral. This was done on an aus Jena Fluoval. It is a vintage biological
"Cancer research" microscope that has been modified for petrographic cross polarized light use. I could go on for many pages about the
160X in transmitted (pass through) cross polarized light
This shows what the material really looks like. This technique will show the vesicles as white while the background is black. I know these
shots are ugly. For those of you who have worked with Xpol you might appreciate the difficulties associated with getting good photos of
material that looks like this. (It gets better!)
This was the most fun I have ever had with a thin section! I hope you have enjoyed the art of these images and this article has shown
you a bit about the micrographic process.