One ton of iron produces one ton of slag
Towards the end of the 19th Century the furnaces of Cleveland were producing 2.5 million tons of pig iron a year.
noun: scoria; plural noun: scoriae
basaltic lava ejected as fragments from a volcano, typically with a frothy texture.“chunks of black scoria”
slag separated from molten metal during smelting.Origin -Late Middle English (denoting slag from molten metal): via Latin from Greek skōria ‘refuse’, from skōr‘dung’. The geological term dates from the late 18th century.