on form:
    event-block is cobblestone
    chance of 3%:
        set event-block to diamond ore
    chance of 2%:
        set event-block to emerald ore
    chance of 10%:
        set event-block to lapis ore
    chance of 10%:
        set event-block to redstone ore
    chance of 15%:
        set event-block to gold ore
    chance of 20%:
        set event-block to iron ore
    chance of 25%:
        set event-block to coal ore