I got a set of single convex yunzi stones back in November with my bamboo board and bowls. When I got them, they were in pristine condition, and I have a lot of extras (I ordered 2 sets, and between them, I got 25 extra black stones and 13 extra white stones.) But in the past month, I've managed to break quite a few of the stones, and I have no idea how it happens. I've dropped stones, and they've bounced off the board, bounced off other stones, bounced off the floor, and that doesn't seem to even phase them, but every once in a while, I'll find a stone at the bottom of the bowl with about a third of it broken clean off. I have no idea how it happens, and it seems to be happening more and more frequently . I'm always very careful when I'm putting the stones away and when handling the bowls with the stones in them, but I keep finding broken stones. Any ideas how this could happen (how the stones could survive being dropped 3-5 feet onto tile floor unscathed, but break from being moved around in the bowls a little)? Also, would anyone know of any extra precautions I could take to help prevent this? And on a strange note, all of the stones that have broken so far have all been black stones. No casualties from the white stones yet....

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If Chess was invented by man, then Go was invented by God.

It sounds like you are more careful about how you put them away in their bowls than you are when you use them in play...

But to answer your question, it could just be the constant pressure placed upon stones at the bottom turns minor stress flaws into actual cracks that then separate.

They're probably not unscathed. Being dropped onto the floor probably weakens them considerably, and that's (part of the reason) why they break.

More than thirty years ago, the guy who taught me to play go insisted we play on the floor if it was made of a hard material like tile or brick. We always played over carpeted or wooden floors when sitting at a table.

He taught me one other thing: avoid dropping one's stones. See the board, see the move, see the branches, and decide. Reach into the bowl, grasp the stone firmly, place the stone exactly where planned.

Hesitating leads to changing one's mind which leads to hovering which leads to the dreaded and terribly vulgar bomb tesuji or a shattered stone should it hit a hard floor.

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David Bogie, Boise ID
I play go, I ride a recumbent, of course I use Macintosh.

bogiesan, you were very lucky that he taught you this excellent habit.

Interesting ... in my 2nd online game someone took the time to share a similar habit. He said to leave your hand off the mouse until you make your move ... similar theory. No potential for bomb tesuji though.