On mine of stone:
    chance of 10%:
        set event-block to chest
        set {skrztnka.%player%} to location of event-block
        loop 5 times:
            add a random item out of all items to event-block
        exit loop
        wait 20 seconds
        remove event-block
On chest open:
    location of event-block is {skrztnka.%player%}:
        wait 5 seconds
        remove event-block
        delete {skrztnka.%player%}