The titanium minerals of commercial importance are rutile and ilmenite (_vide_ Part I. pp. 57 and 77). The former, the pure titanium dioxide, is of fairly wide distribution, but ilmenite occurs in far greater quantities, forming deposits of enormous dimensions, especially in America, as, _e.g._ in New York Co. and Quebec. Owing to its high melting-point and relatively low specific gravity, metallic titanium can only be incorporated with molten steels with the greatest difficulty, and for this reason alloys of titanium and iron, known technically as ferro-titanium, are usually employed for the treatment of steels. For the preparation of ferro-titanium, ilmenite of good quality is as suitable as rutile, and, of course, far cheaper; hence the latter is only employed for the preparation of titanium salts for use in colouring and mordanting, and for titanium compounds for arc-lamp electrodes, etc. Various processes are employed for the manufacture of ferro-titanium from ilmenite. In cases in which a considerable percentage of carbon is not undesirable, for instance, where the alloy is required for the treatment of cast iron or of high-carbon steel, the mineral is reduced directly with carbon in an electric furnace; the ferro-titanium so obtained usually contains from six to eight per cent. of carbon. For pure iron-titanium alloys, the process worked out by Rossi[609] is used in America almost entirely. Ilmenite is charged into a bath of molten aluminium, heated electrically; the mineral is at once attacked, with formation of iron, in which the titanium dissolves as reduction proceeds. This process may also be used for reduction of rutile, if scrap iron is added to the aluminium bath, to allow of the formation of the required alloy. In Germany, the Goldschmidt or ‘thermite’ reaction is largely employed; powdered ilmenite is intimately mixed with the calculated quantity of aluminium powder, reduction being started as usual by means of a fuse of magnesium ribbon imbedded in a small quantity of barium peroxide. [609] _Elect. chem. Ind._ 1903, ~1~, 523.