Where did the rocks that broke out in the Monkey King in the Journey to the West come from?

First of all, the Monkey King didn't jump out of the stone directly, but the stone cracked and laid a stone egg. Stone eggs are weathered into monkeys.

As for the origin of the immortal stone, it is not clear in the original work. I only heard that there is a fairy stone on the top of the mountain in Guo Hua. Since the opening, it has been naively displayed, and the sun is shining. After a long time, it means to be well informed. Inbred elf cells. One day, it burst and laid a stone egg. The wind turned it into a stone monkey.