Minecraft is expanding again. Mojang have announced that the game's new 1.3 update will arrive on August the 1st and will bring with it "A huge number of changes". It's been a bit of a wait since the last Minecraft update, but Mojang say that's because they've been making some significant structural changes to Minecraft's engine, they've "kicked out single-player, and made it a shell on top of multi-player," which brings us one step closer to mod support, and will ensure that any tweaks to multiplayer will work in single-player as well.
According to the Mojang website 1.3 will include "lots and lots of bug fixes" and performance enhancements. Those will be needed however, as the new singleplayer/multiplayer combined build will be more performance intensive. According to Mojang "When playing single-player, the game needs to be able to both simulate and emulate the world, which take many more CPU cycles."
There's lots of new features too. Emeralds and emerald ore are now in the game, and function as a currency. You can use them to trade with villagers and get new items. You can write in books to leave stories for other players and set tripwires to trigger monster traps. There's new stairs, half slabs and cocoa plants plus tweaks to lots of other items. Plus you now get magic orbs from mining and smelting, and can choose to start the game with a 'bonus chest' of starter items, if you're sick of spending your first night covering in a hole.
Sadly the Mod API won't be available with this update, but Mojang say it will be coming soon, "Throwing out single-player was the first step in order to make the API possible, and that's done now. We decided to release 1.3 without the API, because otherwise it would be an even longer wait for a Minecraft update."
If you want the full patch notes, which are enormous, you can read them on Reddit .