Minecraft wiki entry for Block_of_Copper, associated text: Let a be the number of all nearby unwaxed copper blocks, and b be the number of nearby unwaxed copper blocks that have a higher oxidation level. We derive the value of c from this equation: c = b + 1⁄a + 1. We also let the modifying factor m be 0.75 if the copper block has no oxidation level, or 1 if the copper block is exposed or weathered.[1] Then the oxidation probability is mc2.