Aluminum Ore (also spelled Aluminium Ore in some language versions) yields Aluminum, needed to craft various recipes in Galacticraft.
Aluminum Ore can be found in deeper mining - anywhere between the layers of Y=0 and Y=45 - with a frequency of 18 clumps within every chunk. It is generated in clumps of 7 blocks on average.
Other mods mostly do not include Aluminum Ore or Aluminum ingots, so these are not always going to be processable in other mods.
Thermal Expansion - if installed with Galacticraft - offers Pulverized Aluminum and Aluminum Ingot, so that your Aluminum Ore can be doubled in the Pulverizer.
Galacticraft 4 build 139 (February 2018) adds full Aluminum Ore compatibility with the IndustrialCraft 2 Macerator and also the Applied Energistics 2 Quartz Grindstone, Actually Additions Crusher, and EnderIO SAG Mill. So there is Aluminum Dust and (if IC2 is present) also Crushed Aluminum Ore and Purified Crushed Aluminum Ore.
If processed fully through three stages of IC2's ore processing machines, 1 x Aluminum Ore yields the following:
- 2 x Aluminum Dust
- 2 x Tiny Pile of Iron Dust
- 1 x Tiny Pile of Titanium Dust
- 1 x Stone Dust
These match the real-world mining products of Bauxite, the main aluminum ore found on Earth.
The Tiny Pile of Titanium Dust side-product can be crafted into Titanium Dust and then smelted into Titanium Ingot and compressed into Compressed Titanium. It will take nearly one full stack of Aluminum Ore (54 blocks of ore) to produce 3 x Compressed Titanium. That's enough to craft 1 x Titanium Pickaxe. So, if you have a full IC2 ore processing setup including the Thermal Centrifuge (which requires a Mining Laser) then you can obtain small amounts of Titanium, enough to craft a few of Galacticraft's advanced titanium items, without even travelling to the Asteroids. It will be a slow path, to create Titanium Leggings requires two full stacks of Aluminum Ore.