196. Metallurgy
The use of metals in America falls into three stages. The peripheral and backward areas, such as Patagonia and California, and those parts of the Tropical Forest in which nature had denied a supply and remoteness had shut off trade, did wholly without metals.
In the areas of medium advancement, like the Northwest, Southwest, and the ancient Mound Builder region of the Ohio Valley, native copper was beaten out into sheets, trimmed, bent, gouged, and engraved. It was not smelted from ore nor cast. Its treatment was thus essentially by stone age processes. Gold, silver, and other metals were not used; iron only sporadically when it could be obtained in the native metallic state from a fallen meteorite. The supply even of copper was rarely large. It flowed in trade, much like precious stones among ourselves, to the wealthier groups of nations able to part with their own products in exchange for this substance prized by them for jewelry and insignia but rarely made into tools.
The third stage is that of true metallurgical processes, and is confined to the three Middle American areas. Here, copper, gold, silver, and so far as they were available tin and platinum, were sought after and worked. Copper at any rate was extracted from its ores by smelting; all the known metals were fused and cast, both in permanent molds and by the method of melting wax out of a single-time mold. Wire was beaten or drawn out; gold leaf and acid plating practised; and welding, hardening by hammering, and self-soldering were known. Alloys were made: copper-tin bronze in Bolivia and the south Peruvian highland, whence its use later spread north, perhaps being carried as far as Mexico (ยง [108]); copper-arsenic bronze and copper-silver alloy on the Peruvian coast; copper-gold in Colombia and Mexico; copper-lead bronze in Mexico.
Nowhere, however, was metal the standard material for tools, which continued to be mostly of stone or wood. Metallic tools and utensils, especially knives and axes, were not altogether rare in the bronze region of South America. The superior hardness of bronze as compared with copper no doubt proved a stimulus in this direction. But Maya temple-cities were built with stone tools, and the Aztecs cut and fought with obsidian. In general, metal remained treasure or ornament. There were not even the beginnings of an iron culture anywhere in the hemisphere.
In the larger outlines, the history of American metallurgy is thus simple enough, as something developed late and never diffused beyond the central region of intensive culture. As to the sequence of use of the several metals and processes, on the other hand, rather little has been ascertained. It seems that in these matters South America might have been somewhat in advance of Mexico, both in time and in degree of attainments. The age of the metallurgical arts in Middle America must not be underestimated. In spite of their relative recency, they can hardly have been less than several thousand years old.