abundant ancient metal, iron was the last to become available due to its melting point (see above), including requiring tools made from alloys such as bronze to work in quantity. Other comparably abundant elements, such as titanium (approximately 4,400ppm) and aluminium (approximately 83,000ppm), were not available until the modern era. This was due almost entirely to the huge quantities of energy required to purify ores of these elements. Energy requirements and tool availability were, therefore, the primary limiting factors affecting an ancient civilisation's ability to access metals, rather than those metals' relative abundances. See also Timeline of chemical element discoveries Ashtadhatu, the eight metals of Hindu alchemy History of metallurgy in the Indian subcontinent History of metallurgy in China Metallurgy in pre-Columbian America Copper metallurgy in Africa Iron metallurgy in Africa Symbolism The practice of alchemy in the Western world, based on a Hellenistic and Babylonian approach to planetary astronomy, often ascribed a symbolic association between the seven then-known celestial bodies and the metals known to the Greeks and Babylonians during antiquity. Additionally, some alchemists and astrologers believed there was an association, sometimes called a rulership, between days of the week, the alchemical metals, and the planets that were said to hold "dominion" over them. References Further reading http://www.webelements.com/ cited from these sources: A.M. James and M.P. Lord in Macmillan's Chemical and Physical Data, Macmillan, London, UK, 1992. G.W.C. Kaye and T.H. Laby in Tables of physical and chemical constants, Longman, London, UK, 15th edition, 1993. Metals History of metallurgy