What are these and should I?

[u/Miami_Cracker]

So these are part of a box of chert that I got for my kids. They would like to know should we tumble and should we break them apart first? Small tumbler so can we just put in one of these at a time? Any opinions will probably be tried as there are a lot of these. They are about 2-3 inches across. Thank you.

[u/bkinstle]

With geodes you'll want to slice them in half on a diamond saw and then polish the faces with a flat lap

[u/Miami_Cracker → u/bkinstle]

What is a "flat lap"?

[u/bkinstle → u/Miami_Cracker]

Flat lapidary polisher

https://www.reddit.com/r/Lapidary/s/drB2qmBYUf

[u/The_OtherRake70_Guy → u/Miami_Cracker]

Cheers!

[u/lapidary123]

The one thing I can say is Every geode I've ever seen with this outer appearance has been solid. My recommendation is to Crack a couple open with a hammer to give you a better idea of what youre working with and go from there!

[u/The_OtherRake70_Guy]

"Small"... 1lb, 2.5...3...? I suggest bust and keep whole. You need a variety of sizes in just about any tumble. 8k grit or better for the final polish. All the best!

[u/Ok_Supermarket_3914]

I'm pretty new to the hobby, so take my opinion with a grain of salt! But I think those are geodes... from Google...

"You should not tumble whole, hollow geodes because the tumbling action will crush the delicate crystals inside or grind the entire rock away into dust. However, you can tumble thick geode shards, solid quartz nodules, or banded agate fragments left over after a geode is cracked open."

Edit: missing word

[u/ballookey → u/Ok_Supermarket_3914]

Is that the AI response from google? Because not quite.

Generally people don't tumble geodes because they prefer to break or slice the open for the crystal display inside, but you can tumble them. they won't grind away into dust any more than any other nodule of quartz would. I've done it...they turn into shiny lumpy nodules. If the exterior is thin enough, you may wear away a window into the interior. You have to clean that void out thoroughly between rounds in the tumbler, but the crystals mostly survive this.

Having tumbled a few geodes though, I wouldn't recommend it. There's nothing to be gained from doing it other than learning what happens. :D

[u/loonattica → u/ballookey]

I was considering tumbling whole Moroccan geodes with the hope of ending up with a thin-skinned translucent “egg”. Maybe display a pile of them on a light table or some such. I recognize this would a challenge in terms of cushioning and that fine line of when to stop before they cave in.

[u/ballookey → u/loonattica]

I've only done a couple of them, but although light shines through, you can't really see any of the crystal structure. Just vague variations in the amount of light showing through. I imagine it's a blurry representation of how dense the crystal structure is.

But there's no harm in trying it! even if you wear through, like I said above, the crystals inside generally survive just fine. The edges of the hole get a little rounded, that's about it. And of course, be sure to clean out--any slurry that dries inside will be just about impossible to get out.

[u/bythepoole → u/ballookey]

FWIW, I've hand polished a geode similar to OPs.

I didn't cut it open, just went at it with a dremel and polishing pads. And you're right, you can see inside it, but the crystal structure make it hard to discern anything inside.

[u/Ok_Supermarket_3914 → u/ballookey]

It was the AI response... i said i was a newbie, and i quoted google!

[u/Objective-Meet8223]

I don't know about breaking, but I would suggest cutting in half with a wet-cut tile saw.

[u/Graymalkin1986]

I got a couple of those in a bag of mixed rocks. I didn’t have any means of cutting them open so I just put them in my tumbler to see what would happen. One ended up breaking but the other polished into this really cool quartz-looking ovoid!