GOLD 



271 



in the 1960's encourages belief in the existence of 

 other unrecognized deposits. The geologic environ- 

 ment of these deposits is still not completely under- 

 stood but is the subject of much current research; 

 for instance, the geochemical similarity between 

 these deposits and certain modern hot-spring depos- 

 its in New Zealand that contain as much as 85 ppm 

 gold and 500 ppm silver has been noted recently by 

 Weissberg (1969). Enough is known, however, to 

 indicate that very large areas underlain by favor- 

 able host rocks remain untested; the most likely 

 area for further discoveries is the Antler erogenic 

 belt in central Nevada and its inferred extension in 

 southern Idaho north of the Snake River Plain 

 (Roberts, 1960, 1966). 



BYPRODUCT GOLD 



Gold is a common minor constituent of base-metal 

 ores and may be recovered when these ores are 

 smelted and refined. Such ores, although data on 

 their gold content are very sparse, appear to contain 

 0.001-0.025 ounce per ton (0.04-0.9 ppm). Despite 

 the very low gold content, gold production from 

 these deposits is significant because of the large 

 tonnages mined each year. Currently, byproduct 

 gold accounts for 40 percent of the total United 

 States gold output, and 19 of the 25 largest gold- 

 producing mines in the United States yield gold only 

 as a byproduct (Hoyt, 1971, p. 533) . Of the byprod- 

 uct production, 80 percent is from copper ore, and 

 the rest is principally from complex ores of lead, 

 zinc, and copper. Salt Lake County, Utah, which 

 contains the large open-pit copper mine at Bingham, 

 yielded more than half of the byproduct gold pro- 

 duced in the United States in 1969. 



Precise figures on the worldwide production of by- 

 product gold are not available, but this source prob- 

 ably accounts for 5-10 percent of the total world 



output. Byproduct gold constitutes a significant 

 part — 15 percent or more — of the production from 

 several major gold-producing countries, including 

 Australia, Canada, Japan, Nicaragua, Peru, and the 

 Philippines. 



In recent years, byproduct gold has been a steady 

 source of supply in the United States, and it is 

 expected to continue to be so into the future. Any 

 change in production will be controlled largely by 

 output of copper and, to a lesser extent, of lead and 

 zinc. Changes in the price of gold will have a negli- 

 gible effect on production from this source. Similar 

 considerations apply to byproduct gold output in the 

 rest of the world. 



RESERVES AND RESOURCES 



Many estimates of U.S. and world reserves and 

 resources of gold have been made, and a few are 

 given in table 51. World reserves of gold total about 

 1 billion ounces, of which 60 percent is in South 

 Africa. At the present rate of production, world re- 

 serves would be exhausted in 20-25 years. U.S. gold 

 reserves are 50-80 million ounces, about half of 

 which are in byproduct ores. The remainder are 

 mostly in disseminated and lode deposits. 



In addition to reserves of gold in the ground, 

 large amounts are held by governments and banks 

 as official reserves and by speculators and other 

 private holders. Government and bank holdings total 

 1.3 billion ounces, of which about 292 million ounces 

 was in the U.S. Treasury at the end of 1971. The 

 quantity of gold in the hands of speculators and 

 others, although difficult to estimate, is probably of 

 the order of 1 billion ounces. Clearly, the reserves 

 of gold already mined are considerably larger than 

 those of unmined gold. 



The U.S. gold resources shown in table 51 are 

 mostly conditional resources. Hypothetical and 



Table 51. — Reserves ' and potential resources ' of gold (in millions of ounces) in the world as estimated in several sources 



of data 



B 



source of data 3 ^^^^ ^^^^ ^^^^^ ^^^^^ ^^^ ^^^ 



United States '9 399 50 '53 '244 82 



South Africa ___ — ) ) ] ^° 



Canada III ^^ 



Australia .._ ._. > 950 > 300 > 600 10 



Other non-Communist countries III ^^ 



Communist countries (excluding Yugoslavia) J j ) 200 



World total _.. ... 1,000 353 844 1,000 



'Reserves: Identified deposits from which minerals can be ex- A13); C, Ageton (1970, p. 677); and D, U.S. Bur. Mines (1972, p. 61). 



tracted profitably with existing technology and under present economic ^ Exclusive of byproduct gold, 



conditions. ^ Producible at $35 per ounce. 



2 Potential resources: Identified mineral deposits not profitably re- ''Producible at 1968 price — about $40 per ounce. Includes 30 million 



coverable with existing technology and economic conditions, and undis- ounces of byproduct gold, 



covered mineral deposits whether of recoverable or subeconomic grade. "^ Producible at prices up to $145 per ounce. Includes 30 million ounces 



= A, U.S. Bur. Mines (1967, p. 5); B. U.S. Geol. Survey (1968, p. of byproduct gold. 



