Copper is the 16th rarest ore in the Quarry. It is succeeded by silver.
Since copper is the most common ore in the Quarry, it has the lowest sell price in the Quarry, $12. It has the same sell price as granite, so when mining in granite, players tend to ignore copper. It is less expensive than obsidian, so it is avoided in what little part of obsidian contains it. Rare ores cannot replace copper, unlike other common ores, making it useless to leave behind.
Dave's In-game description: A common ore in the earth, can be used for creating tools. It is most common around -75 blocks deep.
-Although the badge description states it, there is no possible way to mine above the surface. This is an obvious deliberate typo.
-It has a very similar color to granite, making it somewhat difficult to make out in that layer.
-Copper is arguably just as common as silver, although it has a lower selling price.
-The lowest depth at which it can be obtained is at -780.