ECONOMIC GEOLOGY 435 Figure The cliffs facing the Gulf of Carpentaria in Queensland, Australia, and a working face in the vast expanse of pisolitic bauxite Scale shown by white penknife near the centre Photos: GR Davis for over 2000 years as tools, ornaments and weapons Supplies of metal increased when smelting was discovered to reduce the natural ores of Cu, Pb, Sn and later Fe into metal The ownership of valuable metals and other minerals, such as salt, begat wealth and power The rise and fall of ancient civilizations is intimately bound up with the riches derived from control of mineral resources, and the historical theme continues to this day For example the shift of power and control of trade routes from the Persians to the Greeks was greatly influenced by wealth from the newly discovered Laurium Ag-Pb deposits near Athens, and then gold in Macedonia Finance was available to build a powerful navy that enabled Themistocles to conquer Xerxes at the decisive battle of Salamis in 480 bc The Greeks enjoyed a golden age of philosophy and art; the mining revenues assisted Philip of Macedonia to establish his dominance, and for his son Alexander the Great to finance the first campaign in his great Middle Eastern conquests about 330 bc In that same region, the 20th century has witnessed the global economic and political impact of the discovery and development of major oilfields upon the countries of the Middle East Figure (with logarithmic scale on the vertical axis) illustrates how world demand for mineral products over the last 150 years of the industrial age has been met by production growth rates that exceed even the ‘explosive’ growth rate of world population Annual production rates for the basic industrial materials iron and petroleum have grown dramatically, and the production rate of copper, a primary base metal, has increased a hundredfold During the Figure Over the past 150 years, world demand for mineral products has exceeded the ‘explosive’ growth in population, shown on a logarithmic scale twentieth century newer metals such as nickel became industrially important, and aluminium, once rare and precious, reached production rates exceeding that of copper, and at a lower cost per tonne Many other ‘new’ elements continue to emerge in response to the growth of modern high-technology industry For instance, demand is now growing rapidly for indium (mine production about 340 tonnes in 2002), which is needed for making flat-panel electronic displays as used in mobile telephones and plasma-screen televisions World population is increasing, and the average per capita demand for mineral products, while heavily skewed by industrialized Western world usage, is also increasing Economic geology plays an integral part in meeting this challenge to the mineral resource base of the world