11Treasured since ancient times for its permanence and beauty, gold has emerged j'.n the late twentieth century as an essential industrial metal. Electronic computers could not function reliably without gold for their complex circuitry. Men could not have reached the moon without gold to shield their equipment.and spaceships from the sun's rays. Turbine blades on jet aircraft would disintegrate without high performance gold solders to join them to rotors. A host of other appl i cat i.ons- of gold have made it indispensable to the industrial Not only is gold important to industry, but it retains a unique status amo~z all commodities as a long term store ofvalue". (West, 1976).
The Earth's crust is estimated to have an average gold content of 0.0035 grams per tonne or 3.5 ppb (West, 1976). The average gold content of common igneous rocks is from 1.5 ppb {or rhyolites to 6.6 ppb for ultramafics and the gold content of sediments falls within the same range (Crocket, 1974). It thus requires processes capable of concentrating gold 2000 to 3000 times above its crustal abundance to form an ore body.
Gold mining has been an industry of mankind for almost 6, 000 years. The earliest gold miners were the Sumerians, who were .working deposits in present day Iran by 3800 B.C., and the Egyptians, who had organized gold mining on a significant scale by 3500 B.C. (Poss, 1975). Approximately
90, 000 tonnes has been recovered over this time, sufficient only to form a 17 metre cube, but because it is virtually indestructible almost all of it is still in circulation (Fig. 1).

World production in 1977 was probably 1, 300 tonnes (42 million ounces), and was dominated by South Africa.and the U.S.S.R. The uncert• ainty relates to production from the U.S.S.R., and the problem is evident in Figure 2 which shows the estimates of U.S.S.R. production by the United States C.I.A. and Consolidated Gold Fields (C.G.F.). Detailed U.S.S.R. production is available for 1974 and totals 421 tonnes (13 mill•ion ounces) suggesting that the C.G.F. estimates are correct. Production
from the Witwatersrand deposits of South Africa, which has totalled 32,000 tonnes, peaked in 1971 and is expected to decline significantly over the next 30 years (Fig. 3). The U.S.S.R. has been a major gold producer since the 19th century (Emmons, 1937); it has produced 14,000 tonnes to date, and is likely to remain an important producer for many years.

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