An industrial complex in the Stone Age
Deep within the Amazon rainforest, in the same mineral-rich highlands of the Serra dos Carajás known today for the world's largest iron ore mine, lies evidence of a much older industry. Here, Paleoindian peoples established a significant mining and tool-production complex over 10,000 years ago. These early hunter-gatherers systematically quarried one of the region's other treasures: large, exceptionally clear veins of hyaline quartz, also known as rock crystal.
The site is not a single quarry but a series of open-pit mines, workshops, and processing areas spread across the area. Archaeological investigations, often prompted by modern geological surveys, revealed that these ancient miners were highly selective. They specifically targeted the highest-quality, glass-like quartz, bypassing lower-grade material. The scale of the operations shows a long-term, organized effort to extract and process this valuable stone. Evidence from similar-aged sites suggests that quarrying was a central activity for these early societies, providing materials for both daily life and social exchange. The name "Asurini" is a modern association, referring to an Indigenous group currently living in the broader region of the Xingu River basin.
Tools, techniques, and trade
The technology used at the Carajás crystal mines was effective. The miners were skilled geologists, able to identify and follow the most promising quartz veins. To break the hard rock, they used heavy stone mauls, or hammerstones, some weighing many kilograms. They also likely employed fire-setting—heating the rock face with intense fires and then rapidly cooling it with water to create fractures. This allowed them to break off large quartz blocks for processing.
At adjacent workshop sites, these blocks were systematically reduced into smaller, more manageable pieces called cores. From these cores, specialized craftspeople would strike off sharp flakes to be shaped into tools. The primary products were bifacial projectile points, masterfully worked spearheads that are hallmarks of Paleoindian cultures across the Americas. The choice of translucent rock crystal was not purely functional; its aesthetic qualities show the objects had social or ritual importance. These finished crystal points, along with raw material, entered long-distance trade networks that connected different groups across the vastness of early Holocene Brazil. The presence of these distinctive artifacts far from their source shows a complex social world of interaction and exchange that existed thousands of years before the arrival of Europeans.