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Icbp

Rock cutting and polishing

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Icbp

Hi everyone

 

I recently got a large sandstone block (~20cm x 20cm x 20cm) which is like a shell deathbed (see pics). There's a layer of weathered material on the surface but underneath it's a nice piece. I was wanting to try and clean it up and do something nice with it. My ideas were to either (1) square it off and polish the block or (2) Square it off and slice it into multiple thin slabs (maybe 2-3cm thick) which could then be polished. I'm not sure if it's bad practice to slice up a fossil or not.

 

Anyway, I was hoping someone might be able to give me some advice on what tools would be appropriate for cutting a block this size or how to go about polishing the block afterwards. Alternatively, if anyone has any other cool ideas for it I'd be keen to hear them. 

 

Any advice would be really appreciated!

 

Cheers

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WhodamanHD

It isn't ideal, but in this case your probably not going to get a good prep on the shells, so this my justify the cut and polish. These are however very very old (in most cases, millions of years) so most who collect fossils leave them how they are (or prep them out to see them better), this preserves them and makes them look quite nice.  It's not particularly uncommon to find fossil shells in sandstone. Good luck to you, whatever choice you make!

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JohnBrewer

That's the sort of rock I would cut and polish. As I only have a tile saw and an angle grinder MY only option and the one I would take is to cut in two or three (difficult to judge size of your rock with no international recognised scale, hint hint). Rockhounds with the correct gear would use a rock saw, outa my price range. You can then start grinding with perhaps a file to start with to roughly get it flat and then the hard work begins. Use emery sheet/cloth on a flat board and grind away. Start with a coarse grade until really flat and go finer. Use water as you grind too. You'll need to go down to 1200 grit at least. I've used very fine aluminium oxide powder mixed with water using float glass as a substrate to grind on. You can finish using lapidary polishing compound or if you want a quick finish use a very dilute Paraloid/acetone mix. 

 

@ynot amongst others, may have other (better) ideas as he's a mineral guy as well as a fossil collector. 

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ynot

Welcome to TFF!

Cutting and polishing a rock is an art.  You will need a rock saw to cut it. To get a flat surface polished the best method is with a flat lap (a diamond disk grinding unit.). Trying to polish by hand will be hard and time consuming.

Hard to tell from the pictures, but the stone looks porous (water soaks in rather than runs off.). This will make it impossible to get a good polish.

You could cut it and then paint it with a clear lacquer, but it will look artificial.

 

I think this piece will be best left as is.

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