Aluminum Ore generates in the Overworld, once per chunk. It spawns in veins of 6 and between heights of 64 and 0. It can be smelted into Raw Aluminum or melted in a Smeltery to produce 2 ingots of Liquid Aluminum. Five ingots of Aluminum melted with 2 ingots of Iron and 2 ingots of Obsidian (1 block) will yield 3 ingots of Alumite, a very hardy and useful material.
Aluminum Ore can also be used for Aluminum Brass, which can be used in casts just like Gold.
Raw Aluminum is the product of smelting Aluminum Ore or Gravel Aluminum Ore in a furnace. It can be melted down in a Smeltery to make Molten Aluminum, which can then be used to make the alloys Aluminum Brass or Alumite. It can also be made into ingots using the Ingot Cast, or into blocks using an empty Casting Basin.