ABSTRACT
Economists claim that it pays to mine high-grade mineral deposits first and lower-grade deposits later. Moreover, it is often assumed that relatively few ore bodies remain to be found that would be of higher quality than those already discovered. According to this line of reasoning, in the course of a nation's mining history the average grades of ore mined will decline as the higher-grade deposits are gradually depleted. The example most commonly cited as evidence of this sequence of events is the drop in the average grade of copper ore mined in the United States—from more than 3.0 percent around 1900 to about 0.5 percent today. It is often inferred from such evidence that countries with a significant history of mining have been forced to exploit lower-grade ores and are at a competitive disadvantage vis-àvis countries with a shorter history of mining.
