While slags are generally used to remove waste in metal smelting, they can also serve other purposes, such as assisting in the temperature control of the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal.In nature, iron, copper, lead, nickel and other metals are found in impure states called ores, often oxidized and mixed in with silicates of other metals.
Slag is drawn off the furnace just before the molten steel is poured into ladles for ingotting.
Ferrous and non-ferrous smelting processes produce different slags.
When the filtering process is complete, the remaining slag granules, which now give the appearance of coarse beach sand, can be scooped out of the filter bed and transferred to the grinding facility where they are ground into particles that are finer than Portland cement.
During the Bronze Age of the Mediterranean there were a vast number of differential metallurgical processes in use.
Any sandy component or quartz component of the original ore automatically carries through the smelting process as silicon dioxide.