Mojang has updated the mobile version of Minecraft (subtitled Pocket Edition), adding furances and smelting to the mix. Now you can either find or build block type yourself. You can also grow your own trees by collecting saplings from cut leaves, and find Diamond, Gold, and Iron ore. You can then smelt ore into various objects and tools to continue exploring the world. In other words, the game is basically Minecraft, only on the mobile iOS platform.
Minecraft is available for US$6.99 in a universal version from the App Store right now. There's also a free version with limited features, but it doesn't include this latest update anyway, so if you want to play the real thing on a mobile platform, you must shell out seven bucks.