Tim points me to an article at Chilean newspaper El Mercurio[es] (first page, article 1, article 2), where the archaeological finding of the century maybe is discussed. This finding is nothing less than what can be the oldest ever mine, dug by pre-farming peoples of what is now Northern Chile some 12,000 years ago.
The mine is located in the municipality of Taltal, Antofagasta, and the date has been confirmed by analysis in three independent laboratories from the USA and Poland. In spite of its antiquity, the article mentions it is not the oldest of the world, even if it is the oldest one known in America: the record oldest mine is in South Africa (40,000 years ago), followed by Australia (30,000) and Greece (15,000).
The Taltal mine was used to extract iron oxide, ochre mineral used for decorative and ceremonial purposes. In that time the area was occupied by the peoples of the Huente-Lauquén culture, the first settlers of the Northern Chilean coast, who lived largely on fishing.
Besides the mine, more than a thousand stone hammers have been found. The hammers, apparently lacking handles, were the main tool used to work in the mine. They did not even make use of fire to weaken the rock, it seems.
Even if it is not the oldest mine, it does seem the largest one for any pre-Neolithic culture known so far. In this sense, it raises many questions about how a hunter-gatherer community could muster so many energies for a non-practical purpose of this magnitude.
However, even if the article does not mention it, it is known that fishing communities in some areas did manage to support large populations and enjoy affluent stable economies that allowed for certain levels of collective organization. The best known case are the potlatchs of NW North American natives, other such cases may be the Jomon people of Japan or the Lepenski Vir culture of Serbia and Romania.