I have a friend that owns a 40 pound 10 1/2 inch round geode. He would like to have it cracked open. Both he and his wife say they are interested in have it sawed open (which would be my choice if I owned it). Rather he’s asking what the appropriate method would be. I Googled it and it seems the thought is to use a hammer and a chisel. Can anyone offer a better suggestion?
I’m definitely not a geode expert, but I have a background in ceramics engineering, and we used to cleave large ceramics back in the day when I was in the business. basically we’d draw where we wanted the crack to run (scribe a circle around) then hit it with a grinder disk cutting about 1/4-1/2 inch into the piece. once you have the basic route you want, GENTLY start tapping it with a metal chisel and hammer working your way evenly around the part… eventually, it’ll crack open and //mostly// follow where you wanted it to crack… but sometimes not! so YMMV
There is a vendor out at Scarborough Faire that sells geodes that they crack on site. They’ve got some sort of guillotine that they smack the geode with, and it cracks in half. I think that their geodes seem to be some sort of soft-ish rock to begin with, though. May make it easier to smack them that way.
I’d be inclined to go with Ian’s suggestion. We’ve got some saws, but they seem better for slicing a portion off, rather than halving a big piece like that. I’m not at the space, but I don’t think that there’s 5.25" inches of clearance on the far side of the blade on the oil saw. Plus, on the oil saw, you’ve got to secure the piece by gluing it to a board. I haven’t used our wet saw, so I’m not sure how it works, so far as securing the piece. You might be able to true up the edge if it cracks too weirdly.
thanks to both of you for the response.
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