[meteorite-list] Cleaning a heavy iron meteorite

From: Michael Gilmer <meteoritemike_at_meteoritecentral.com>
Date: Fri, 11 Nov 2011 12:56:33 -0500
Message-ID: <CAKBPJW8978Xa-Kk+SiVFM2d80Gr1Ldg7uZknRGuvMCOnB_dVTQ_at_mail.gmail.com>

Hi Abe,

You already got some good advice from the List. That is a weathered
stony chondrite and not an iron. That brownish coloration is a
coating of "desert varnish", which is a thin layer of mineral
desposits that build up over a long period of exposure to the
elements. Some less experienced collectors (and a few dealers) will
mistakenly describe this coating as "fusion crust" or remnant crust.
In fact, as someone else already said, the fusion crust was
sandblasted away long ago. No amount of sanding or cleaning will
replace the lost crust. The desert varnish coating is very thin, and
if you aggressively clean it, it will abrade away and leave you with
nothing but bare rock, which is less attractive than desert varnish.

If the stone is covered in caliche (which yours is not), then the
caliche is very stubborn and difficult to remove. Some people will
try acids or corrosives, but the most effective method to remove it is
mechanical means or lots of elbow grease and a wire wheel or wire
brush. Smaller stones covered in caliche can be tumbled in a rock
tumbler with steel shot and alcohol - this will remove the majority of
caliche, but will also remove the desert varnish if you are not
careful. Typically about 8-10 hours in the tumbler is all that is
needed, any longer than that and the stone's appearance will be
altered in a detrimental way.

Best regards,

MikeG

-- 
---------------------------------------------------------------------------------
Galactic Stone & Ironworks - Meteorites & Amber (Michael Gilmer)
Website - http://www.galactic-stone.com
Facebook - http://tinyurl.com/42h79my
News Feed - http://www.galactic-stone.com/rss/126516
Twitter - http://twitter.com/galacticstone
---------------------------------------------------------------------------------
On 11/11/11, Guenther <abe.guenther at mnsi.net> wrote:
> Hi all,
>
> A year ago I found a large heavy iron meteorite. When I found it the color
> was a dark brown. In my attempt to bring out the true color, I decided to
> use a dremel tool with a fine wire brush bit to clean it. The dremel brush I
> used was extremely soft and gold in color and it turned slightly gold in
> color. So, I bought a soft stainless steel wire brush and now it turns grey
> when I brush it. What is the best way for me to clean it to get the true
> color?
>
> Here are the original images after I used the gold color brush:
>
> http://aguenthe.mnsi.net/NM1.jpg http://aguenthe.mnsi.net/NM2.jpg
> http://aguenthe.mnsi.net/NM3.jpg http://aguenthe.mnsi.net/NM4.jpg
>
> Thanks,
>
> Abe Guenther
>
>
>
> ______________________________________________
> Visit the Archives at
> http://www.meteoritecentral.com/mailing-list-archives.html
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
>

Received on Fri 11 Nov 2011 12:56:33 PM PST