This is smelted with rich gold ores, notably those containing tellurium, for white metal or regulus; and by a following process of partial reduction analogous to that of selecting in copper smelting, " bottoms " of impure copper are obtained in which practically all the gold is concentrated.
It is a silvery white metal which burns on heating in air.
Pure potassium is a silvery white metal tinged with blue; but on exposure to air it at once forms a film of oxide, and on prolonged exposure deliquesces into a solution of hydrate and carbonate.
Magnesium is a silvery white metal possessing a high lustre.
Aluminium is a white metal with a characteristic tint which most nearly resembles that of tin; when impure, or after pro longed exposure to air, it has a slight violet shade.