[meteorite-list] Polishing Stones Answers

From: tett <tett_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:56 2004
Message-ID: <3A578858.A6DDA93A_at_bmts.com>

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Wow!&nbsp; This list is great!
<p>I have received many replies to my queries regarding getting saw marks
off my meteorite slices.&nbsp; Thanks to all that responded.
<p>I have also received some posts asking me to forward the responses.&nbsp;
I have summarized some of them below.
<p>With these answers I have been able to greatly improve and enhance the
features of some of my slices.&nbsp; I had a piece of Red Deer Hill which
was polished too much.&nbsp; By coarsening the polish I was able to bring
out some dark shock veins (I believe) of Ringwoodite!
<p><b>From Rob Elliot</b>
<p>"Don't be in too much of a rush to polish all of your stones. An ordinary
chondrite that has a certain degree of weathering will darken drastically
after polishing.....you'll highlight the metal flake but you'll lose chondrule
definition and contrast, as they tend to merge into the surrounding matrix
and become less visible. Sometimes a few saw marks are preferable in a
slice, opposed to a highly polished slice that hides all it's features,
so choose with care :-)
<p>If you do want to polish some of them, you can do it by hand. Use isopropyl
alcohol and something like a 600 grit abrasive sheet to polish out the
worst saw marks, then progressively work towards 1200 grit or finer....work
<br>piece in a figure 8 motion and keep it rinsed with plenty of isopropyl
alcohol during polishing. Some people complete the process with a polishing
compound for a very high gloss finish, but a mirror finish like that is
<br>to my taste."
<p><b>From Dorothy Norton</b>
<p>"We just noticed your post on saw marks. My husband Richard Norton says
the best way to deal with saw marks on a meteorite is not to buy those
slices. With that said, he has written about this very subject and other
<br>defects in the next issue of Meteorite! magazine - Centerpiece. This
includes brief instructions on how to grind them by hand. All you need
is plenty of patience.
<p>PS. There is no 'back' side to a meteorite slice. Both sides should
be finished. That way you get the most from your specimens."
<p><b>From Eric Olsen</b>
<p>"It is easier with a machine, but not necessary.&nbsp; I use a Highteck
8 inch lap wheel to remove saw&nbsp; marks and flatten the meteorites,
but everything after that is hand sanded on a flat surface using sheets
of sandpaper.&nbsp; The wheel is 180 grit and the sandpaper is 220, 320,
and 600.&nbsp; You could use sand paper to get the saw marks out it will
just take longer.
<br>Some words of caution.&nbsp;&nbsp; Some chondrites should not be polished.&nbsp;
Selma for instance will polish black and all the chondrules will disappear.&nbsp;
If the chondrules start to disappear it is possible to go back a grit,
but you must
<br>sand in a back and forth motion or the surface will look badly scratched."
<p><b>From John Gwilliam</b>
<p>"Go to the hardware store and buy a few sheets of each of the following
grits of silicon carbide (wet&amp;dry) sand paper - black stuff.&nbsp;
220, 400, 600, 1500.
<p>Cut the sheets into quarter sheets.&nbsp; Starting with the coarsest
(220), place it on a very flat surface, preferably a piece of glass.&nbsp;
Hold the specimen with your fingers and apply a modest downward pressure
as you move it back and forth on the paper.&nbsp; Move to a fresh section
on the paper as the spot you are using loads up with dust.&nbsp; Once you
can no longer see any saw marks, wipe the specimen with a clean paper towel
with a bit of anhydrous alcohol on it.&nbsp; This will remove the grains
of grit that can contaminate the next finer sanding steps.&nbsp; Repeat
with the 400, 600, and 1500 grit and you will have a finely polished specimen
that is also flat."
<p><b>From John Sinclair</b>
<p>"Crystalite makes both motorized and hand polishing material for stones.
I have been using their equipment for years with excellent results. Their
home page is <A HREF="http://www.crystalite.com">http://www.crystalite.com</A>.&nbsp; Their parent company's page
with diamond hand pads is
<br><A HREF="http://www.abrasive-tech.com/Pages/Specialty.html">http://www.abrasive-tech.com/Pages/Specialty.html</A>
<p>I would check with Crystalite for their polishing hand pads if the diamond
ones are too expensive. I didn't see them on their site but I know they
carry them."
Received on Sat 06 Jan 2001 04:04:24 PM PST

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