When a sticky piston retracts an amethyst crystal in any growth stage, attached to the piston's head, the crystal will both produce particles and sound as if it had broken, however the block will remain in place. This doesn't happen if the crystal isn't connected directly to the piston head. The issue also occurs if the amethyst is connected via slime block, however only if it's aligned with the piston's direction.
How to reproduce:
Place a sticky piston
Place any stage of amethyst crystal on the piston face
Extend and retract the piston
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Can confirm.

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They also dont break when being pushed. When pushed by a piston, they will move on to the next block, and not break. If it is pushed into a hopper, the piston wont activate.