[meteorite-list] R Chondrites and Magnetism

[bernd.pauli at paulinet.de]

Tom concluded:

> So, most R's have enough metal to be
> attracted to a powerful enough magnet

Careful, please. I'd like to add the little word "just",
leave out the word "most" and replace it by "some":

> Some R's have  j u s t  enough metal to be
> attracted to a powerful enough magnet ...

This sounds better because almost all the iron is oxidized and
also FeNi (nickel-iron) is extremely rare (only some tens of parts
per million!)

In his Cambridge Encyclopedia, O.R. Norton writes on p. 116:

"There is almost no free iron metal (a few grains here and there) ..."

> ... if I can find out why R's have so little metal.

Oxidation (water was the oxidizing agent):

Step 1: extensive aqueous alteration on the R parent body
Step 2: dehydration (removal of water) + thermal metamorphism


Best wishes,

Bernd