[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> <!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> Wow! This list is great! <p>I have received many replies to my queries regarding getting saw marks off my meteorite slices. Thanks to all that responded. <p>I have also received some posts asking me to forward the responses. 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. I had a piece of Red Deer Hill which was polished too much. 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 the <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 not <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 preparation <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. I use a Highteck 8 inch lap wheel to remove saw marks and flatten the meteorites, but everything after that is hand sanded on a flat surface using sheets of sandpaper. The wheel is 180 grit and the sandpaper is 220, 320, and 600. You could use sand paper to get the saw marks out it will just take longer. <br>Some words of caution. Some chondrites should not be polished. Selma for instance will polish black and all the chondrules will disappear. 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&dry) sand paper - black stuff. 220, 400, 600, 1500. <p>Cut the sheets into quarter sheets. Starting with the coarsest (220), place it on a very flat surface, preferably a piece of glass. Hold the specimen with your fingers and apply a modest downward pressure as you move it back and forth on the paper. Move to a fresh section on the paper as the spot you are using loads up with dust. 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. This will remove the grains of grit that can contaminate the next finer sanding steps. 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>. 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." <br> <br> </html> Received on Sat 06 Jan 2001 04:04:24 PM PST |
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