Dross

"Dross" typically refers to waste material or impurities that are produced during the processing of metals, particularly in metallurgy. It often appears as a scum or residue that floats to the surface during the smelting of ores, and it can include both non-metallic materials and unwanted metals that need to be removed to obtain a purer product. The term can also be used more broadly to describe something regarded as worthless or of low quality, such as inferior products or items that have little value.