Before going to Firestone Lake, it's best to collect some more snowballs at Nortinka. There will be a few Octoroks when you enter. Defeat them and go to the raft, then right and up. There's a boulder in your way. Bomb it and enter the cave. After talking to Gwonam, use the lantern. Throw the snowballs at the fireballs. On the way down, you'll find Grapple Berries. Take them and keep going to see a large, still fireball. Throw a snowball at it and take the Fire Diamond.
Items to Obtain: