My old rock tumbler was leaving my agates scratched up and dull

Lisa Jones · 2026-04-07T04:40:04.486972+00:00

I was getting really bad results with my agates from Lake Superior, even after the polish stage. I read online to add a tablespoon of borax to the final polish grit. Did that, ran it for another two days, and the difference was crazy. The stones came out with a real shine, no more tiny scratches. Has anyone else found a good fix for a cheap tumbler?

julia2865mo ago

I always thought borax was just for laundry. My dad used it in his old tumbler back in the 90s and I figured it was an outdated trick. After reading your post I tried it with my last batch of Montana agates. The shine is completely different, like a wet look instead of just smooth. I guess some old methods still work best. What kind of polish grit were you using when you added the borax?

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the_dylan5mo ago

What grit size are you running before that polish stage? Sometimes the scratches come from not stepping down fine enough first.

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jesseb202mo ago

I ran 60/90 silicon carbide then 500 then 1000 before the polish. The borax trick was with 8000 grit aluminum oxide and it made everything pop.

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