Poor Ore

Poor Ore is a type of ore from Railcraft. There are five types of poor ore: iron, copper, tin, lead, and gold. These ores were created so that the update containing the Electric Locomotive and all its related blocks could be created out of copper, tin, and lead. They are unlike normal ores, as they are smelted into two nuggets per ore, rather than a single ingot. They cannot typically be duplicated.

They have fairly standard spawn mechanics.