Aluminium

Aluminium is a metal and an element added by various mods.

Vanilla
on the Minecraft Wiki

GregTech 5
The main source of Aluminium is Bauxite Ore, but it can also be acquired from electrolyzing various other dusts as well. Aluminium Dust cannot be smelted in a regular Furnace and must be smelted in a Blast Furnace or an Industrial Blast Furnace to be smelted into ingots. Ingots and plates are mostly used as replacements for Refined Iron ingots and plates, but are required in some other recipes as well.

GregTech 6
GregTech 6 has very complicated aluminium deoxiding.

Immersive Engineering
Aluminium is created by smelting Bauxite Ore.