Ya dystopian rocks which moth people hatch out of

[Emily]

Ya sci fi dystopian children playing on stones which turn into eggs that moth people hatch out of

Read in the late nineties but book could have been older. Might have been in a textbook.

[Joseph]

This is likely The Green Book, by Jill Paton Walsh.

"I climbed up it and it shrugged itself and made me fall off."
Jason looked at it with interest, biting a biscuit.
"Its shape looks different from before," he said.
So Pattie stared at it too. And while they were all looking,
a crack appeared in the stone. It just tore open a
little way, and there was an inside like a piece of
wet gray velvet."