Copper

Copper is an elemental Allomantic metal that allows one to hide Allomancy. A misting or mistborn burning copper generates a 'coppercloud' which hides Allomancy from being detected by Bronze. The Allomancer also becomes immune to emotional Allomancy, though this effect is not felt by those around them.

Copperclouds are generally not piercible but those with exceptional strength may do so. A Duralumin pushed Bronze, a bronze Hemalurgic spike, or being more powerful to a large degree (such as being a Mistborn granted the power by Larasium compared to a Seeker with diluted blood lines).

A Copper Misting is called a Smoker.

In Feruchemy it is used to store memories. By forgetting things and transferring them to the Metalmind to be able to recall it later though the time it spends in memory rather than in the metalmind tarnishes it. Ruin can influence memories stored in a metalmind.

A Copper Ferring is called an Archivest.