ore from the Lake Superior district. It yields a heavy pigment of value. One reason paint compounded from it wears so well is because of its specific gravity. It is almost a pure ferric oxide, and requires a small proportion of oil to prepare it for application in a paint.

Artificial oxides of iron are sold under a variety of names, such as Indian, Turkey, Venetian red, etc. If properly made, some are stable pigments. They are made under a variety of processes, but usually by calcining copperas. Years ago, Venetian reds were burnt ochres, and, therefore, produced more durable paints than the copperas reds of the present day, which latter are apt to contain traces of sulphuric acid, and frequently excesses of land-plaster and powdered limestone.