Smelting residue is a byproduct of the smelting process, which is used to extract metals from ore. The four crossword solutions for this term are SCORIA (6 letters), DROSS (5 letters), SLAG (4 letters), and speiss (6 letters). SCORIA is a type of volcanic rock that is formed during the smelting process. DROSS is a mixture of metal oxides and other impurities that form on the surface of molten metal. SLAG is a glassy material that forms when metal is smelted and is composed of silicates and other minerals. Speiss is a metallic residue that is produced during the smelting of certain ores.