Silver in comparison with gold is of rare occurrence in nature in the metallic state. It is not found in the sands and gravels of rivers, but has to be sought for in mountain regions, where it is embedded in mineral veins. In these veins, too, it rarely occurs at the surface, like copper in the Lake Superior district of America, or in the outcrops of veins, as there, where it may once have been present as metal, it has usually been converted into chloride, by the traces of chlorine as sodium chloride invariably present in rain. Its occurrence is hence limited to the deeper deposits, where the ores are but little altered, and even there it is almost always in the form of delicate filaments or thin leaves, and very rarely massive, so that, without being first melted, it could not be fashioned into the simplest objects. An exception to its occurrence in these forms is found in the Kongsberg mines in Norway, where large masses, ranging in weight from 68 lb. to 1,537 lb. avoir., have been taken from the underground workings. For the above reasons silver has played no part in the culture of early man, and indeed it has never been found, as we shall see later, in association with his remains until subsequent to the time when he had first become acquainted with copper or bronze.