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NWA 869 More Features


Thank you for the baggie of NWA 869 slices. I’ve gone through them all at least twice with a 10X loupe. I found a few interesting things to show you. Some of them we talked about last time. I have to admit that it took me a while to make some of these pictures. Metal and other shiny things have to have the light just right. The first few here, though, were pretty straightforward.

These successive slices have nice clean boundaries between rock types. Not a rare thing in brecciated stones, just a good example. Here, the light colored rock at the top is the more metamorphosed, the dark at the bottom is the lesser altered by heat.
These slices faced each other. You know that, you made the cut that divided this cement-gray fine grained inclusion. Except for a little metal it is nearly featureless. I wonder what researchers will tell us this material is.
This fine grained material is slightly more coarse. Metal seems to be only around the edges.
A green crystal. What do you think? Pyroxene?
This chondrule and its internal structure stand out nicely. Pretty good for no thin sectioning and only a fine sanding. It looks like there is one chondrule completely inside another.
The shiny white is iron–nickel metal, the shiny bronze is troilite, iron sulfide. You have to have the light at the right angle to see these.
More detail. It’s tricky getting the light right under a microscope.
These colors – blue, purple, orange, yellow – appear to be on a patch of troilite. They probably represent different thicknesses of oxides on the surface of the sulfide. This is similar to the colors seen on a steel knife blade while tempering it. My guess is that after you cut and sanded this slice something in the crack spread and promoted the changes.

Troilite FeS
Pyrite FeS2
Pentlandite (Fe,Ni)9S8

Armored chondrules. I love them.

– John

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