Copper slag is a by-product of the copper smelting process. It normally accumulates in huge piles near the smelter, but it can be used as an abrasive in sand blasting and as a coating on roof tiles. As a guide for modelling the production of copper slag with Trainz industries, assume that 100kg of copper ore will produce 10kg of copper concentrate, which after smelting will yield 3kg of copper metal and 6kg of copper slag.