Items such as sheet metal, treated lumber, corn syrup, and plastics are examples of

Items such as sheet metal, treated lumber, corn syrup, and plastics are examples of processed materials.

Processed materials are materials which have been refined or built by humans from raw materials. Processed materials are different from component parts as they become part of a finished product and don't retain their original identity.
Ceramic is a processed material. You have to add several materials, heat them, sinter them and then you get ceramic.