I was just browsing through some of the posts on Joes Skyrockcafe website
when I ran across a post from a collector who was unhappy with the Radio
Shack etchant for iron meteorites. He claims to have sanded a Campo down to
#400 but could not get a Widmanstatten pattern, although he did get a
beautiful pattern using the traditional Nitric method.
My son, Jim, and I posted an article in the November 2002 issue of the
Meteorite Times about preparing and etching irons using Ferric Chloride
(which is the same material as used in the Radio Shack etchant). The method
has been used widely since that time with outstanding success by many and
with superior results, so there is now an undisputed 8 year positive
history. Etches show more contrast and subtle details come out more
readily, and fears of ferric chloride use have been put to rest as the
specimens are not rusting and crumbling. In fact, they do just as well if
not better than when etched with nitric. (But that is a topic for another
day.)
I think the problem of the person in posting his negative experience was
that after grinding down to a #400 grit that he did not then polish out the
surface. Unlike preparing an iron to etch with nitric acid, the surface
wants to have a highly reflective mirror-like surface before etching. As we
say in the article, however, every meteorite is different and can react
differently to different circumstances, so he may have just had an unusual,
but uncommon, experience. He may have a very different experience with a
different Campo. (I have many Ferric-etched slices of Campos in my personal
collection and they are all doing well.)
Ron Hartman
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