From the first link:
There have been incredible, but totally unsubstantiated, claims made as to the time and manpower required to create the ancient copper pits and as to the amount of native copper that has actually been mined. Beginning with Drier and Du Temple in 1961 and Mertz in 1967, through Sodders in 1990, figures of .5 to 1.5 billion pounds (yes billion, not million) have been put forth. Sodders postulates "it is believed that as many as 10,000 miners, labored some 1,000 years, in an estimated 10,000 Copper Range pits". Drier and Du Temple get to their figures with the following faulty assumptions in their 1961 work "Prehistoric Copper Mining in the Lake Superior Region": "If one assumes that an average pit is 20 feet in diameter and 30 feet deep, then it appears that something like 1000 to 1200 tons of ore were removed per pit. If the ore averaged 5% or 100 pounds per ton then approximately 100,000 pounds of copper were removed per pit. If 5000 pits existed, as earlier estimates indicated (and all are copper bearing), then 100,000 pounds per pit in 5000 pits means that 500,000,000 pounds of copper were mined in prehistoric times- all of it without anything more than fire, stone hammers and manpower. If the ore averaged 15% copper and if more than 5000 pits existed, then over 1.5 billion pounds of copper were mined". Where did these figures come from, who created them, based on what evidence?

One has to ask the obvious question, where did all this mined copper go? Some scholars would have us believe that the vast majority was taken by Phoenicians, Berbers, Minoans, Bronze Age Europeans or Vikings in a huge international copper trade centering in the Lake Superior Region. Where is the archeological evidence to support these theories? The truth is that it does not exist. There are no identified community or camp sites, no burial remains, and no identifiable artifacts to support any of these theories. Are we to believe that these foreign miners were so environmentally friendly that they took all their garbage from daily living back with them, along with the copper, and what about their dead, did none of them die here? If there had been mining operations sufficient to produce 500 million to 1.5 billion pounds of copper there would be significant archeological evidence to substantiate it. All of this evidence does exist to demonstrate that the indigenous peoples were the ones who mined the copper and fashioned it into implements, weapons and ornaments, over a period of as much as 7000 years.

Sodders figures of 10,000 miners laboring for 1000 years in an estimated 10,000 pits are pure unsubstantiated bunk. Who counted the 10,000 miners? The Copper Complex copper pits were actually worked much longer than 1000 years, proven by archeological evidence. As for the estimated 10,000 pits, who estimated that number and based upon what data? There has never in recorded history been a comprehensive study and tally done of the number of pits, what is the evidence for this "estimated" number of copper pits?

The estimates put forth by Drier and Du Temple are easily debunked. They start with the errroneous and unsupported assumption that the average pit was 20 feet in diameter and 30 feet deep. An average based upon what sample? No study of these ancient copper pits has ever determined an average size. Few, if any, pits have ever been reported as deep as 30 feet (and this is Drier & Du Temples average depth, so some must be deeper), when in fact many ancient pits or trenches barely scratched the surface by more than a few feet. Twenty feet seems to be the limit on depth of known ancient copper pits and these are few in number.

The assumption of 5000 pits has no supporting documentation as a comprehesive study of the number of pits has never been undertaken and published. Their 5% to 15% copper content is flawed since content can run from zero to 100% (mass copper). The amount of copper in the country rock isn't constant or regular, an expensive fact learned by many early modern mining companies. All of the numbers offered up by Drier and Du Temple are based solely on conjecture, with no basis in fact.

The link to Doug's site now brings up the following warning: This web page at www.ramtops.co.uk has been reported as an attack page and has been blocked based on your security preferences.

IIRC the article also raised similar concerns about the validity of the calculations.

"The Stone Age did not end for lack of stone, and the Oil Age will end long before the world runs out of oil"

-- Sheikh Zaki Yamani