Ore
A naturally occurring mineral deposit from which a metal can be extracted profitably.
Unit
Dimensionless
In depth
Every ore is a mineral, but only minerals with a high enough metal content to be worth processing count as ores, so the definition shifts with metal prices and extraction technology. Ores are classified as oxides, sulfides, carbonates or halides.
Examples in the real world
Bauxite for aluminium, haematite for iron, galena for lead, and chalcopyrite for copper.