Minecraft wiki entry for Caves_%26_Cliffs, associated text: Copper blocks are used for crafting and storage.
Made with nine copper ingots.
The stonecutter can be used to craft the different copper block variants.
Only cut copper can be used to make stairs and slabs.
Example:
Made with four copper blocks.
Cannot be turned back into regular copper blocks or copper ingots.
Develops a patina of pale green copper carbonate over multiple stages, exposed, weathered, and oxidized.
Honeycombs can be used to make waxed copper, which does not progress beyond the patina stage it has at the time. The wax can be scraped off with an axe, but it does not drop the honeycomb.
Axes can be used to undo the oxidisation stages one at a time.