The Wealth of Nations by Part 1 Chapter 11 Page 204

computed, the whole quantity of the one metal, it would seem, cannot, in the Spanish market, be disposed of so advantageously as the whole quantity of the other.

The tax, indeed, of the King of Portugal upon the gold of the Brazils is the same with the ancient tax of the King of Spain upon the silver of Mexico and Peru; or one-fifth part of the standard metal. It may, therefore, be uncertain whether to the general market of Europe the whole mass of American gold comes at a price nearer to the lowest for which it is possible to bring it thither than the whole mass of American silver.

The price of diamonds and other precious stones may, perhaps, be still nearer to the lowest price at which it is possible to bring them to market than even the price of gold.