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Antarctic Meteorites and Chipping
Jim Hurley schrieb:
> Thanks, Bernd, for the fascinating Antarctic meteorite stories.
I am glad you liked them. Thank you.
> In several places, it was mentioned that small specimens were
> 'chipped' rather than sawed, presumably to avoid losses and
> minimize contamination.
> Do you know how this was done? A sharp blow with a hammer? A chisel?
On page 9 of the Smithsonian Contributions to the Earth Sciences, No.
23, there are some photos plus explanatory notes, among them the
following: "...Meteorite being chipped inside the processing cabinet;
the c h i s e l and bowl are of stainless steel."
> I'm just wondering how they controlled
> the 'chipping' to prevent 'crushing'.
They were not always successful. Look at some selected passages from my
US Antarctic database:
01) When the meteorite was cleaved it broke along fractures, thus
producing only one chip with unweathered material exposed.
02) The stone chipped easily, revealing a highly oxidized broken face.
03) This meteorite was very coherent and had to be pried apart along
complete fractures during chipping.
04) Abundant minute interior fractures cause the stone to break into
smaller than desired chips.
05) The sample is friable and easily crumbled when trying to obtain a
chip for thin sections.
06) ... obtaining a chip from other than along a pre-existing crack was
nearly impossible.
07) Chipping this small stone was impossible. Sawing revealed an
interior with many clasts discernible in the dark gray matrix.
Best regards,
Bernd
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