DIFFERENT KINDS OF PIG IRON, ETC. 147 higher. This brand of iron is cast in chill molds or magnesia sand and is used chiefly in the open-hearth furnace to make steel. Silvery or ferro-silicon iron is sometimes made with all coke, and then again with coal and coke. The silicon ranges from 6.00 to 16.00. It is derived from high silicious ores and excessive fuel to give high temperatures in the furnace. Mottled and white iron is made with both coke, anthracite, and charcoal fuels. Its silicon ranges from .10 to i. oo, sulphur from .05 to .30, manganese .10 to 1.50 or over, phosphorus .03 to .50 and upward, and usually high in carbon. These irons are generally the off product of a furnace that has not been working well, and are used for hard or chilled castings, or at rolling mills to be mixed with gray forge irons.efly used at steel works for making steel and in foundries for ingot moulds, and can often be well used in the place of u foundry iron " in general castings not requiring good or extra fluid metal to run them.