As the Navajos have no silver mines in their country, they depend largely for their material upon Mexican silver dollars worth about 48 cents in United States money. These are melted and then molded, or else cut and hammered into the desired forms. Sometimes, United States half or quarter dollars are used in this way, although such silver costs more than twice as much, because of its worth as currency. Before silver was freely used, copper and brass were bought at the trading posts and favored as materials; a supply of these metals being often secured by melting down parts of the kettles or pans furnished to the Indians by the United States Government, or else bought from white settlers. Some old Navajo silversmiths assert that the art of working silver was introduced from Mexico about sixty years ago, toward the middle of the last century. About this time a Mexican silversmith named Cassilio came to the Navajo country and taught his art to a Navajo blacksmith called by his people Atsidi Sani, or the “Old Smith.” Cassilio is said to have been still living about 1872. An artisan considered to be one of the best, if not the very best of the Navajo silversmiths of our day, who is called Beshlagai Ilini Altsosigi or the “Slender Silversmith,” originally learned his art from Mexicans. The fact that Lieut. James H. Simpson, who explored the heart of the Navajo country in 1849, has nothing to say about silversmithing, although he details very fully the various arts and industries of the Navajos, goes far to prove the truth of the statement that Navajo silversmithing dates from a later time.[50]