The mines were mere wells, not very deep; with horizontal workings into the obsidian where it was very good and in thick layers. Round about were heaps of fragments, hundreds of tons of them; and it was clear, from the shape of these, that some of the manufacturing was done on the spot. There had been great numbers of pits worked; and it was from these “minillas,” little mines, as they are called, that we first got an idea how important an element this obsidian was in the old Aztec civilization. In excursions made since, we travelled over whole districts in the plains, where fragments of these arrows and knives were to be found, literally at every step, mixed with morsels of pottery, and here and there a little clay idol. Among the heaps of fragments were many that had become weathered on the upper side, and had a remarkable lustre, like silver. Obsidian is called _bizcli_ by the Indians, and the silvery sort is known as _bizcli platera_.[11] They often find bits of it in the fields; and go with great secrecy and mystery to Mr. Bell, or some other authority in mining matters, and confide to him their discovery of a silver-mine. They go away angry and unconvinced when told what their silver really is; and generally come to the conclusion that he is deceiving them, with a view of throwing them off the scent, that he may find the place for himself, and cheat them of their share of the profits—just what their own miserable morbid cunning would lead them to do under such circumstances. [11] The book-name for obsidian is _itztli_, a word which seems to mean originally “sharp thing, knife,” and thence to have been applied to the material knives are made of. Obsidian was also called _itztetl_, knife-stone. But no Indian to whom I spoke on the subject would ever acknowledge the existence of such a word as _itztli_ for obsidian, but insisted that it was called _bizcli_, which is apparently the corrupt modern pronunciation of another old name for the same mineral, _petztli_, shiny-stone. [Illustration: Mexican Arrow-heads of Obsidian.]