[meteorite-list] Re: Looking for Buried Iron-Shale with a Metal Detector

[Notkin]

> Exactly what is "meteoritic shale"?. I have never heard this term 
> before.


Dear Steve:

Meteoritic shale (sometimes "meteoric shale") is a term used to 
describe a highly weathered iron meteorite. Weathering could be caused 
by a meteorite having been on the earth for a very long period of time 
(i.e. Wolf Creek) or partially decomposing in an area where there is 
moisture (i.e. Nantan).

This "shale" is sometimes referred to as oxide, in the sense that the 
iron has decomposed or terrestrialized to the point where most or all 
of the original metal has turned to iron oxide. It is less dense and 
less magnetic than a solid iron meteorite (hence Paul's question about 
what might be involved in hunting for shale).

The Santa Catharina and Monturaqui meteorites are two irons which, I 
believe, have only ever been found as shale. The Canyon Diablo, and 
Odessa craters have both produced large amounts of shale and I expect 
there are many others.

I have seen grapefruit-sized "shale balls" of Canyon Diablo and Nantan 
which have been cut in half to reveal a very thick weathered rind of 
shale, with a metallic core. I find it to be very interesting material.


Regards,

Geoff N.