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 Lerasium compared to a Seeker with diluted blood lines).
A Copper Misting is called a Smoker.
Known Smokers (excluding Mistborns): Clubs (perishes during the 2nd book)
In Feruchemy it is used to store memories. By forgetting things and transferring them to the Metalmind, a Feruchemist can recall these memories at a later date exactly as they were originally seen. Memories 'tapped' from a coppermind degrade whilst in the mind, and must only be used for short amounts of time to reduce the risk of corruption. It is known that metaphysical beings, such as Ruin, can affect the contents of a coppermind.
A Copper Ferring is called an Archivest.