of Obsidian; shown in two aspects; Mexico. 4. Leaf-shaped Knife or Javelin-head; obsidian: from Real Del Monte. 5. Spear-head of Chalcedony; one of a pair supposed to be spears of State: found in excavating for the Casa Grande, Tezcuco. (This peculiar opalescent chalcedony occurs as concretions, sometimes of large size, in the trachytic lavas of
Cortes found the barbers at the great market of Tlatelolco busy shaving the natives with such razors, and he and his men had experience of other uses of the same material in the flights of obsidian-headed arrows which “darkened the sky,” as they said, and the more deadly wooden maces stuck all over with obsidian points, and of the priests’ sacrificial knives too, not long after. These things were not cut and polished, but made by chipping or cracking off pieces from a lump. This one can see by the traces of conchoidal fracture which they all show.
The art is not wholly understood, for it perished soon after the Conquest, when iron came in; but, as far as the theory is concerned, I think I can give a tolerably satisfactory account of the process of manufacture. In the first place, the workman who makes gun-flints could probably make some of the simpler obsidian implements, which were no doubt chipped off in the same way. The section of a gun-flint, with its one side flat for sharpness and the other side ribbed for strength, is one of the characteristics of obsidian knives. That the flint knives of Scandinavia were made by chipping off strips from a mass is proved by the many-sided prisms occasionally found there, and particularly by that one which was discovered just where it had been worked, with the knives chipped off it lying close by, and fitting accurately into their places upon it.
Now to make the case complete, we ought to find such prisms in Mexico; and, accordingly, some months ago, when I examined the splendid Mexican collection of Mr. Uhde at Heidelberg, I found one or two. No one seemed to have suspected their real nature, and they had been classed as maces, or the handles of some kind of weapon.