Lufilian Arc (Wiki)27 Jul 2019 18:21
"Historically the African copperbelt ores have been more accessible and higher grade than ores from other locations. In 1932 copper percentages in Zambian ore reserves were 3.44% (Roan Antelope), 4.3% (Rhokana) and 4.14% (Mufulira, Chambishi and Baluba). This compares to 1.41% on average for copper ore reserves in the United States at that time. Additional advantages are that the mines mostly contain sulphide ores, which are comparatively easy to concentrate and smelt, and that labor costs are low.[13] As of 2010 the African copperbelt provided about 25% of the world's copper and about 80% of its cobalt. It also has major zinc and lead deposits."
It seems that nowadays majors are happy with 0.5% if the ore is there in great quantity, but wouldn't a throwback to the 4%+ grades of old be awesome? :-)