I had heard from a friend about the high metal content of NWA 15468 OC4-melt breccia. It sounded interesting so I decided to check it out.
I bought this 23.6 gram partial slice from always pleasant Eric Twelker at meteoritemarket.com.
In hand it displayed the variety of textures that I had hoped for – high metal, medium metal, distinct chondrules, melt and that light colored mystery clast.
That lefthand side appeared representative. I made this cut diagram for my thin section maker.
The sample fits nicely on the slide with space for my label.
There is no cover slip and with proper lighting it shines nicely.
Let’s look at a few features.
There is plenty of iron around this chondrule and a few bits inside, too. Reflected light.
This is the same chondrule in cross-polarized light, XPL. The teardrop form of the silicates is dark.
Another armored chondrule in reflected light.
The above chondrule in XPL.
This well formed chondrule is near an edge of the sample. Reflected light.
In cross-polarized light and by rotating the filters we could see that this is a cryptocrystalline chondrule.
Along that same edge this large center chondrule displays internal metal between “bars”. The reflective gold-colored material are sulfides.
The above field in XPL better shows three smaller chondrules to the right and below the larger.
The large, light-colored clast is slightly stained but seemingly otherwise unaffected by its surroundings.
It is surrounded by metal but none seems to have intruded.
In XPL we see that the clast is composed of multiple sectors of barred olivine.
Again, in XPL with the filters rotated to a different orientation relative to the sample.
This is a smallish chondrule, 0.45 mm in diameter. There is bleb of metal and sulfide in its center.
Could the chondrule have formed around the metal bleb?
