[meteorite-list] Iron etching

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:07:05 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4E48A_at_US-Torrance.mail.saic.com>

Hi Mark,

> Ok, I gots a pondering problem. And I'd like some feedback.
> I've tried to etch some irons I have, to no avail, yet. I
> would like to know if anyone has etched their own, and how
> polished are the slices?

So far I've played around with etching Campo, Gibeon, Chinga
and various iron fragments that upon etching revealed themselves
to be manmade (i.e. no W-pattern). I've never tried etching
with Nitol; just ferric chloride (which is much faster acting).

I would think that with octahedrites, even a polish to 800 or
perhaps even 600 grit would be sufficient to see a pattern,
but of course it looks better when polished to 1500 or 2000.

> I've tried one I recieved that was polished very brightly,
> and it is now just dull. So, I was also working on another
> myself and ground it flat, then put it to the 1200 grit
> and tried to etch it, but got nothing (it did look better
> than the piece I had bought already polished though).

Was it an octahedrite? I assume you're looking for a Widmanstaaten
pattern and not Neumann lines. The latter are much more subtle
(I've learned from recent experience). Whereast ferric chloride
will etch an octahedrite nicely in only a few seconds, it took
nearly a minute to really see the Neumann lines in a specimen
I recently acquired.

> I'm just about ready to say maybe my nital isn't of the
> correct concentration, but before I dump it into the
> waste bottle I like to hear some insight from others.

Guess it depends on how long you were soaking in it -- Nitol
is pretty slow I understand.

Cheers,
Rob
Received on Tue 29 Oct 2002 12:11:37 AM PST