Most of the polishing compounds that I am familiar with contain more than just crushed walnut shells or corn cobs. Most of them contain at the least a compound called jewelers rouge and some of them other polishing facilitators as well. I don't know the chemistry of these additives but I suspect that they are not benign. I do know that they leave a residue on the polished surface. Plain soil seems a safer pot cleaner to me. I would use these compounds cautiously if at all.
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May I walk in beauty.