Aluminum is the internal enhancement pulling metal. An Allomancer burning aluminum will make all of his metal reserves vanish. Feruchemists can use aluminum to store identity, and when used as a Hemalurgic spike, aluminum steals enhancement Allomancy. It is known as Ralkalest or the unForgeable metal in the Rose Empire on Sel.
Aluminum metal (and some of its alloys) are "Allomantically inert" - they cannot be Pushed or Pulled, and can shield people from emotional Allomancy. Aluminum generates no atium shadows and can create dead zones within cadmium and bendalloy bubbles, where the shielded area is not included within the time bubble. It also interferes with Feruchemical healing, by making it impossible for wounds to heal around the aluminium until it is removed from the body. There is a similar effect on pewter Allomancy.
A aluminum Misting is known as an Aluminum Gnat. Burning aluminum causes the body to instantly metabolize its metal reserves without any other effect. As such, an aluminum Misting serves no purpose and gains nothing from their powers. Since aluminum can shield against emotional Allomancy, those who can afford to, often wear hats with aluminum lining.
It may be possible for an aluminium savant to cleanse their spirit of unwanted effects of Investiture.
An aluminum Ferring is known as a Trueself. Aluminum is used to store "spiritual sense of identity." This ability is not fully understood, and is rarely discussed outside of Terris communities. A Feruchemist who fills an aluminummind to the point where they have no identity and then fills another metalmind is able produce a metalmind that anyone can use. In a similar manner, a Feruchemist may be able to tap another person's metalminds by filling their own aluminummind completely.
Mistborn Adventure Game
In the Mistborn Adventure Game, aluminum stores "personal identity". While a Feruchemist is filling their aluminummind they become, "bland, indecisive, mildly forgettable, and emotionally pliable -- essentially, less defined and distinct as an individual," and their "tastes, opinions, loyalties, and the like," become, "much more flexible." When a Feruchemist taps their aluminummind they become "a more fully realized version of [themselves], reinforcing deeply-held convictions and allegiances, and dramatically boosting self-worth. The Feruchemist becomes resistant to brainwashing and manipulation, including Allomancy, Feruchemy, and Hemalurgy that influences [their] emotions." The Feruchemist also experiences a boost in confidence and recovers from mental hardships sooner.
The Feruchemist also has the effects of the world on their personality undone. Tapping an aluminummind reverts their personality to as it was at some point in the past.
Some Feruchemists will store memories in a coppermind before tapping their aluminimminds to gain a whole new perspective on those memories.
When used as a Hemalurgic spike, aluminum steals enhancement Allomantic powers.
It is possible that encasing Hemalurgic spikes in aluminium may prevent Hemalurgic decay.
Guns and bullets made from aluminum are highly effective (albeit expensive) because they cannot be Pushed, Pulled, or even detected. Aluminum bullets are actually composed of an allomantically inert alloy of aluminum since the ballistics of a pure aluminum bullet would not work.
Around the Cosmere
Items can be Soulcast into Aluminum. It is unknown if the Aluminum can then be soulcast into other Essences. Shardblades are unable to cut aluminum.[nb 1]However, this is only through magical means. If the aluminum is thin enough a Shardblade may cut it purely by virtue of having a sharp edge. 
- The Well of Ascension chapter 5
- (...) Ralkalest is definitely aluminum (...)
— 17th Shard forums - Oct 13th 2015
- The Alloy of Law Ars Arcanum
- The aluminum would not give an atium shadow.
— Theoryland - March 6th, 2014
- If you dropped a speed bubble whose border goes through an aluminum tube, is the inside of the tube affected by the time distortion?
— 17th Shard forums - 2016-05-28
- the wound would not be able to heal around the aluminum, but once the aluminum came out, and was gone from the system, they would be okay.
— Theoryland - March 1st, 2014
- Aluminum has some weird properties on all of the magic systems, not just Allomancy
— Theoryland - Mar 21st, 2014
- Aluminum is apparently magically inert and it can also act as a sink for Investiture.
— 17th Shard forums - Oct 13th 2015
- Annotation for The Final Empire 36
- Shadows of Self chapter 1
- I would say if you burned aluminum, that would kind of have the effect that you are wanting it to have, which is the negating and sucking out, so it's probably safer.
— 17th Shard forums - Oct 14th 2015
- However, on the extreme end of aluminum, I have in the notes the possibility of cleansing the spirit of unwanted effects of other investitures.
— Theoryland - Sep, 2012
- The Bands of Mourning chapter 3
- Nobody has tried that! (It might work.)
— 17th Shard forums - 2017-03-22
- The Alloy of Law chapter 7
- Annotation for The Hero of Ages 74
- The Emperor's Soul - Day 2
- ... [A] shardblade would not cut aluminum.
— 17th Shard forums - 2017-02-03
- ... Err on "no" for now.
— Twitter - 2016-02-03
- Aluminum would stop Shardblades from magical cutting. But if its too thin like foil, a sword...
— 17th Shard forums - 2017-02-07
- Annotation for The Hero of Ages 60
- There is currently no consensus at Team Sanderson, so this WoB is subject to change for now.
It has yet to be reviewed.
|The Metallic Arts|
|Arts||Allomancy · Feruchemy · Hemalurgy|
|Concepts||Metalborn · Snapping · Savants · Metalminds · Twinborn · Compounding · Blessings|
|Constructs||Steel Inquisitors · Koloss · Kandra|
|Base Metals||Iron · Steel · Tin · Pewter · Zinc · Brass · Copper · Bronze · Cadmium · Bendalloy · Gold · Electrum · Chromium · Nicrosil · Aluminum · Duralumin|
|God Metals||Atium (Malatium) · Lerasium · Ettmetal|
|Era 1 books||Mistborn: The Final Empire · The Well of Ascension · The Hero of Ages · (Mistborn: Secret History · The Eleventh Metal)|
|Era 2 books||The Alloy of Law · Shadows of Self · The Bands of Mourning · The Lost Metal · (Allomancer Jak and the Pits of Eltania)|
|Shards||Preservation · Ruin · Harmony|
|History||Classical Scadrial · Final Empire · Catacendre · Elendel · Southern Scadrian|
|Magic||Metallic Arts (Allomancy, Feruchemy, Hemalurgy) · Metalborn · Mistborn · Misting · Savant · Ferring · Twinborn · Compounding · Atium · Lerasium · Ettmetal|
|Other Media||Mistborn Adventure Game · Mistborn: Birthright · Mistborn film · Mistborn: House War|