marekanite, or " mountain mahogany," and makes a pretty stone, which is used for the manufacture of some objects. The mines from which the Aztecs and their successors seem to have obtained the greater part of their obsidian are located in the State of Hidalgo, Mexico, about thirty miles east of Pachuca. The locality is known as the Sierra de las Navajas, or Hill of the Knives. Here hundreds of acres have been worked over, and heaps and ridges of obsidian fragments are continuous for one or two miles. The mining seems to have
	been performed by digging pits from 6 to 20 feet in depth. Large pieces of obsidian were thus obtained, which were shaped into so-called cores, cylindrical pieces of varying diameters. From these, articles of the desired shape were obtained by flaking and polishing. Immense heaps of flakes show that working of the obsidian was carried on here for centuries. Articles made from it are found among the Aztec ruins in Mexico, and as far north as the mounds of Ohio. They are of great variety, and many of them exhibit much skill in workmanship. They include masks, ear ornaments, lip ornaments, spear heads, arrow heads, knives, and razors. Mirrors were also made from the obsidian. To this latter use obsidian was put by the Romans in the time of Pliny. They 181