The last boom in technological innovation for the copper industry occurred in the first two decades of this century, when open pit mining, flotation concentration, and the reverberatory smelter were adapted to porphyry copper ores.

With the exception of leaching-solvent extrac tion-electrowinning, the basic methods of cop per production have remained unchanged for 65  years. Moreover, six of the mines opened be tween 1900 and 1920 are still among the major copper producers in the United States today.

Instead of great leaps forward, technological innovation in the copper industry in the last 65 years has consisted largely of incremental changes that allowed companies to exploit lower grade ores and continually reduce the costs of production. Economies of scale have been real

ized in all phases of copper production. Both ma chine and human productivity have increased dramatically.

This chapter briefly describes the technology for producing copper, from exploration, through mining and milling, to smelting and refining or solvent extraction and electrowinning. The chap ter begins with an overview of the history of cop per technology development. Then, for each

stage i n copper production, it reviews the cur rent state-of-the-art, identifies recent technologi cal advances, reviews probable future advances and research and development needs, and dis cusses the importance of further advances to the competitiveness of the U.S. industry. Figure 6-1

shows flow-sheets for pyrometallurgical’ and hydrometallurgical

2 copper production. Tables 6-1 and 6-2 provide capsule summaries of these processes.

1 PyrometaIIurgy IS the extractIon of metaI from ores anD concen trates using chemical reactions at high temperatures.

2 Hydrometallurgy is the recovery of metaIs from ores using water based solutions.

As early as 6000 B. C., native copper–the pure metal—was found as reddish stones in the Med iterranean area and hammered into utensils, weapons, and tools. Around 5000 B. C., artisans discovered that heat made copper more malle able. Casting and smelting of copper began around 4000-3500 B.C. (see figure 6-2). About  2500 B. C., copper was combined with tin to make bronze—an alloy that allowed stronger weapons and tools. Brass, an alloy of copper and zinc, probably was not developed until 300 A.D.

Copper was first mined (as opposed to found on the ground) in the Timna Valley in Israel—a desolate area believed to be the site of King Solo mon’s Mines (see figure 6-3). The Phoenicians and Remans, who worked the great mines on Cyprus and in the Rio Tinto area of southern Spain, made the early advances in copper explo ration and mining methods. For example, the Ro mans found nearly 100 lens-shaped ore bodies in the Rio Tinto copper district. Modern geologists have found only a few additional deposits, and almost all of Rio Tinto’s modern production has been from ore first discovered by the Remans.

3 At Rio Tinto, the Remans mined the upper, ox idized, part of the ore and collected the copper Iaden solutions produced by water slowly seep ing down through the suIfide ore bodies. When the Moors conquered this part of Spain during the Middle Ages, the oxide ores had largely been exhausted.Learning from the Roman experience with seepage, the Moors developed open pit min ing, heap leaching, and iron precipitation tech niques that continued to be used at Rio Tinto into the 20th century.

In Britain, copper and tin were worked in Corn wall and traded with the Phoenicians as early as 1500 B.C. The Remans brought improved metal lurgical techniques to Britain.