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Met Name

Met Type

Thin Sections

  Iron, IIIAB

TKW 100 kg. Fall not observed. Purchased May 2023, Tindouf, Algeria. Reportedly found earlier in the year on the border between Libya and Chad.


 

Scott writes:

Published in the MetBul April 11, 2024.

Individual: 11040 grams, 310 x 140 x 110 mm, main mass

Full Slice: 228.7 grams, 140 x 110 x 2.5mm

Like the story of the cute puppy at the animal shelter who wants to come home with you, Craig Zlimen posted (see pic 1) on Facebook asking "To cut or not to cut??? This is a really beautiful iron. So, I guess, 11kg... For sale, or it gets... the SAW".

I decided to take this puppy home and acquired a new doorstop (pics 2-4). Besides the overall aesthetics, what was most interesting about this one was a large squarish crystalline inclusion (see pics 5 and 6). It is very hard, so that ruled out troilite, and while glassy/metallic, it didn’t have the needle shape typical of schreibersite. Maybe it was a large diamond inclusion, I fantasized! Craig had two pieces and so I was able to acquire both the main mass individual as well as a slice (pics 9 and 10) from the smaller 8.6kg piece.

Dr. Calvin Alexander, at the University of Minnesota, kindly offered to do an XRF scan on the inclusion surface and it came back as high chromium. Chromite is a common inclusion in many iron meteorite classifications, but usually present as small grains.

To confirm the inclusion composition, with some difficulty I managed to chip off some small pieces (pic 7) and these were sent to Dr. Jennifer Mitchell, also at the University of Minnesota, who offered to do an SEM analysis (pic 8). The result is now confirmed - this is a huge chromite crystal.

Researching large chromite inclusions didn’t turn up much, except for a very relevant paper by Karl Thomas Fehr and Alain Carion describing pseudohexagonal chromite crystals up to 3cm in Saint Aubin, also a type IIIAB. Hard to be sure of the exact dimension of the crystal or crystals without cutting (won’t happen), but the chromite crystal in this NEA 051 seems to be even larger than the one described in Saint Aubin.

Besides the large chromite crystal, Saint Aubin also has very long schreibersite needles, which you can also see in the slice from NEA 051 (pics 9, 10).

I’d welcome comments on chromite inclusions seen in other classifications.

Photos 2-7, 9, 10 copyright Scott McGregor and may be used with attribution.

Photos 1, 8 copyright Craig Zlimen and may be used with attribution.

  Click to view larger photos     #1     #2     #3     #4     #5     #6     #7     #8     #9     #10