There seems to be some interest in this topic so I will add my procedures to the discussion.
I cut everything in pure water (except irons which I rarely cut). It is harder on the saw blades, but there isn't a problem with additives on the slices. When a slice comes off, it is dried on a paper towel and put into a small container of ethyl alcohol. When I have finished cutting that meteorite all the slices are removed from the alcohol and allowed to dry on a paper towel in the sun while the next piece is cut. Nice to have a hot sunny climate most of the year. When everything is cut, it is off to the flat lap machine. When I first started in meteorites most slices were polished on a lapidary wheel and all the edges were rounded over. I hated the look and started sanding everything on a flat granite slab so the slices would be flat all the way to the edges. The lap machine makes things a lot easier. Pieces are lapped on a 220 grit diamond wheel on both sides using water. Lapped pieces are plopped into ethyl alcohol again until a batch is done. They are then put on a cookie sheet, propped on each other so air gets below as well as on top, and baked at 220 degrees for 30 minutes. They are never exposed to water again except for what is in the atmosphere. What happens next depends on the meteorite. I don't believe that all meteorites need to be polished. They need to be lapped flat to remove the saw marks, but polishing is another story. Selma for instance looks awful polished. It is a waste to even polish one side and any polishing beyond the 220 grit flat lap starts obscuring the visible chondrules. So after drying, Selma and others like it, get one more short lap on a dry 220 grit lap wheel. It probably isn't necessary, but I see it as removing any oxidation or surface contamination remaining from the water and ethyl alcohol and leaving a fresh dry surface. Some have mentioned weight loss as a reason for not sanding, but that is almost never a consideration in my sanding decisions. Weighing experiments over the years have shown that of a 15-20% cut loss only about 1-2% comes from sanding and most of that is in the flat lapping which I am doing anyway. So sanding or not sanding makes very little difference in the final weight. On most pieces the difference in final sanding is 0.1 grams or less. When I polish something new I polish up one side of one piece working with "dry" sand paper on my granite slab running through 220, 320, and 600 grits and sometimes 1200. I compare the piece each step of the way with an unpolished piece to see what looks better or shows off the structure better. It is an esthetics decision which I readily admit may or may not match others views. However, the purpose of the slice is to be displayed by somebody and the better it looks the more likely it will find a new home. So it is best to make it look good regardless of any weight loss or time expended finishing the slice. All things being equal the piece gets polished because it removes the lines from the flat lap. If polishing darkens a piece quite a bit usually I will polish one side and leave the other alone so the more natural lighter version can be seen as well. I don't ever put anything on a finished slice. If a buyer wants it coated it is easy for them to do, but not all buyers want things coated so I don't coat anything. I do all sanding by hand because I feel I have better control than on a flat lap. A couple tips for hand sanders (1) always end your polishing with a back and forth motion. Fine scratches left by the sand paper are less visible than with an orbital motion. (2) When sanding allende the CAIs will look dingy. Use a clean 600 grit paper and make a single quick short stroke to clean the CAIs leaving them bright white. Now that I have had the audacity to say not every meteorite needs to be polished those who disagree can start throwing rocks my way, just make them NWAs please. Eric Olson ELKK Meteorites http://www.star-bits.com ______________________________________________ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list