zapins
starting to spend too much on rocks
Member since March 2016
Posts: 116 
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Post by zapins on Oct 30, 2016 20:24:45 GMT -5
I am trying to polish a garnet cabochon. I have cut it into the shape I like and ground it into shape with rough sandpaper and diamond wheels.
The issue I'm having is that the finer grades of sandpaper (400, 600, 800, 1000, 1500, and 2000 grit) which are black in color (aluminum oxide?) do not affect the stone at all. I think they are not hard enough to cut the surface.
I would like to hear what sandpaper brands you use when polishing harder stones so that I can order some.
Thanks.
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Mark K
Cave Dweller 
Member since April 2012
Posts: 2,818
Member is Online
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Post by Mark K on Oct 30, 2016 20:35:46 GMT -5
I am going to guess that you will need diamond.
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zapins
starting to spend too much on rocks
Member since March 2016
Posts: 116
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Post by zapins on Oct 30, 2016 20:36:51 GMT -5
Any decent source for diamond sand paper? The stuff I saw on ebay was crazy expensive per sheet. Or is that normal?
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Post by spiceman on Oct 30, 2016 21:16:34 GMT -5
I order lots of items from McMaster Carr and they carry a diamond paste used for lapping. Don't know the price but it not going to be cheap.
Have you tried a SC wet/dry sandpaper. Just an idea.
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zapins
starting to spend too much on rocks
Member since March 2016
Posts: 116
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Post by zapins on Nov 1, 2016 22:48:58 GMT -5
I bought a set of diamond paste which should arrive by the 7th.
In the mean time I tried out some silicon carbide sand paper as you suggested and it does scratch the garnet, but for some reason I didn't get a good finish from that either. There were still tiny pits in the final polish, perhaps more than I had originally. I'm not sure why. Perhaps the diamond paste will work better.
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Post by spiceman on Nov 1, 2016 23:55:17 GMT -5
Well, some rocks just will not polish.
Maybe try sanding it dry.
And/or using lots of different grades of grit.
All of this is just a guess. Something will work but it could be hard to find the answer.
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