Copper

Copper is the internal mental pulling metal. An Allomancer burning copper is able to hide Allomantic pulses emanating from those around them, and is immune to emotional Allomancy. Feruchemists can use copper to store memories, and when used as a Hemalurgic spike, copper can steal mental fortitude, memory, or intelligence.
The paired alloy of copper used in the Metallic Arts is bronze. It is also a component in duralumin, which is the alloy of aluminum.
== Allomantic Use ==
A copper Misting is known as a Coppercloud or Smoker. When an Allomancer is burning copper, the pulses from nearby Allomancers cannot be detected by most Seekers. Allomancers with a Hemalurgic spike that enhances their natural ability with bronze, genetically more powerful Allomancers, such as those created with lerasium, and bronze savants are all capable of "piercing" a coppercloud. Nicrosil can also allow a Mistborn or a Seeker to pierce a coppercloud for a brief moment; duralumin would also work for a Mistborn. Multiple Smokers burning copper in the same area will make the resulting coppercloud harder to pierce. As few Allomancers have the ability to pierce a coppercloud, Smokers are of central importance when Allomancers are trying to hide. If a Seeker is inside of a coppercloud, they will be unable to receive any pulses, even from those inside of the coppercloud. Copper is the slowest burning metal of the basic eight Allomantic metals.
Copperclouds can also block other uses of Investiture. On Scadrial, this is most commonly seen in its ability to protect the user from emotional Allomancy; protecting others in the cloud's boundaries is very difficult but not impossible. Copperclouds also block other methods of detecting Investiture, such as an Awakener's life sense or a secretspren's ability to sense the use of Investiture. Additionally, a coppercloud can interfere with more passive uses of Investiture; for example, it can prevent a singer from attuning a Rhythm and affects how spren act.
=== Savantism ===
Savanthood strengthens the coppercloud, making it harder to pierce, and is less debilitating for Smokers compared to other metals.
== Feruchemical Use ==
A copper Ferring is known as an Archivist. Copper is used to store memories. This ability drives the core purpose of the Keepers, a group of Terrismen dedicated to preserving knowledge. Since the memories in a coppermind do not degrade with time (although they are vulnerable to Ruin's manipulation while being transferred), it is perfect for the collection of enormous quantities of facts. Keepers often create "index" copperminds to find individual pieces of information much faster.
When an Archivist stores a memory in a coppermind, it immediately disappears from their own memory (although it can be stored at partial strength to allow them to keep a vague recollection, at the cost of the stored memory being weaker). Memories stored in a coppermind are filed individually and are not seen as one whole reserve to the Feruchemist.
The longer a memory sits outside of a coppermind, the more it degrades, though this is due to the brain's own imperfections rather than a result of the magic. As such, Keepers undergo extensive training in memory retention to keep them as pristine as possible.
Copperminds cannot store muscle memory.
=== Compounding ===
Copper is unique among Feruchemical metals in that the individual bits of Feruchemical charge (the memories) are distinct from one another, as opposed to a metal like steel in which no bit of stored speed is discernible from another. Thus the possible effect of compounding copper is unclear. Rashek was said to have had a flawless memory, possibly the effect of copper compounding, though this ability could have just been propaganda or a non-magical talent like that of his uncle Kwaan.
== Hemalurgic Use ==
When used as a Hemalurgic spike, copper steals mental fortitude, memory, and intelligence. 
=== Kandra Blessing ===
The kandra can use a pair of these spikes as a Blessing and call them the Blessing of Presence. Like all kandra Blessings, the Blessing gives the mistwraiths sentience, with the added benefit of mental stability. This capability includes the ability to focus despite physical discomfort or distraction, exceptionally sharp memory, resistance to madness, and the inability to lapse into unconsciousness due to shock. This Blessing also counters at least some of the mental weakness that is caused by Hemalurgy; kandra with this Blessing are much less vulnerable to being controlled by Ruin than others.
== Fabrial Use ==
Copper can probably be used in Rosharan fabrials. Its effect is unclear, although it might be able to negate alerter fabrials, which are made using bronze. It has not yet been discovered by Rosharan artifabrians.
Reachers use copper lines in their ships to communicate between one another.
== Notes ==
es:Cobre