Chert nodule - how to polish?

[Steve in PA]

My sister found this chert nodule on her property in eastern Tennessee. She would like to polish it. Any suggestions?

 

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[Kray Gelder]

That's a cool intact nodule! The rind covering it hides the pristine chert within. I would find someone with a rock saw, and open it up. Maybe a lengthwise cut, then polish the exposed side, if it turns out to be a nice specimen. You don't know what's in there yet. Good luck.

 

[ToddsPoint]

You'd need a diamond grinder and a whole lot of other diamond tools. Plus a ton of time. It ain't like wood! Get a lapidary to cut a slice and polish it for you. Without opening it first, you don't know what's inside. Might be beautiful, might be junk. Gary

 

[Steve in PA]

You'd need a diamond grinder and a whole lot of other diamond tools. Plus a ton of time. It ain't like wood! Get a lapidary to cut a slice and polish it for you. Without opening it first, you don't know what's inside. Might be beautiful, might be junk. Gary

She was thinking of soaking in Borax solution and then hand polishing. I don't think she wants to cut it. I take it tumbling is not an option? But the outer rind might just be too thick for any type of exterior polishing?

 

[DDancer]

Its fairly large and if you want to keep the form without cutting it a large belt sander with several grits of garnet and then emery, plus a bit of time and elbow grease, would work it down fine. A final buff on a wheel for polish would do it. Otherwise a large tumbler if you dont mind loosing some of the form.