Vanádio, manganês, níquel, tântalo e tungstênio em Mumford (1938)

Marsh and Thoreau were primarily concerned with the threatened extinction of the primeval wilderness and the impoverishment and dangers that might arise from the destruction of the forest cover. But other observers in the nineteenth century noted evils equally threatening in other provinces: Stanley Jevons pointed out that at the rate the coal beds were being exploited in the paleotechnic period, the supply of coal would give out within a century or two unless new resources were discovered or more thrifty ways introduced. While new deposits were in fact discovered and improved methods of coal burning reduced the actual consumption per horsepower, the prediction held true in general: for mineral resources, especially energy resources like coal and petroleum and lignite are irreplaceable once consumed. This is almost equally true of the more precious metals [326] and rare-earths upon which so much of modern technology now depends: nickel, vanadium, tungsten, tantalum, manganese. (Mumford 1938:323/6)

MUMFORD, Lewis. 1938. The Culture of Cities. San Diego: Harvest/HBJ.