Smelting waste is a by-product of the smelting process, which is used to extract metals from ore. SLAG, which is four letters long, is a glassy material that forms when impurities are removed from the molten metal. DROSS, which is five letters long, is a mixture of solid and liquid particles that form on the surface of molten metal. SCORIA, which is six letters long, is a dark-colored volcanic rock that is formed when lava cools quickly. All of these materials are considered smelting waste and can be recycled or reused in various ways.