Finally, the susceptibility of gold and silver of being turned from coin into bullion, from bullion into articles of luxury and vice versa, i. e. the advantage they possess as against other commodities in not being tied down to a definite, exclusive form in which they can be used, makes them the natural material of money, which must constantly change from one form to another. Nature no more produces money than it does bankers or discount rates. But since the capitalist system of production requires the crystallization of wealth as a fetich in the form of a single article, gold and silver appear as its appropriate incarnation. Gold and silver are not money by nature, but money is by nature gold and silver. In the first place, the silver or gold money crystal is not only the product of the process of circulation, but in fact its only final product. In the second place, gold and silver are ready and direct products of nature, not distinguished by any difference of form. The universal product of the social process or the social process itself as a product is a peculiar natural product, a metal hidden in the bowels of the earth and extracted therefrom.[114] We have seen that gold and silver are unable to fulfill the requirements which they are expected to meet in their capacity of money, viz. to remain values of unvarying magnitude. Still, as Aristotle had already observed, they possess a more constant value than the average of other commodities. Apart from the universal effect of an appreciation or depreciation of the precious metals, the fluctuations in the ratio between the values of gold and silver has a special importance, since both serve side by side in the world market as money material. The purely economic causes of this change of value must be traced to the change in the labor-time required for the production of these metals; conquests and other political upheavals which exercised a great influence on the value of metals in the ancient world, have nowadays only a local and transitory effect. The labor-time required for the production of the metals will depend on the degree of their natural scarcity, as well as on the greater or less difficulty with which they can be obtained in a purely metallic state. As a matter of fact, gold is the first metal discovered by man. This is due to the fact that nature itself furnishes it partly in pure crystalline form, individualized, free from chemical combination with other substances, or, as the alchemists used to say, in a virgin state; and so far as it does not appear in that state, nature does the technical work in the great gold washeries of rivers. Only the crudest kind of labor is thus required of man in the extraction of gold, either from rivers or from alluvial deposits; while the extraction of silver presupposes the development of mining and a comparatively high degree of technical skill generally. For that reason the value of silver is originally