A Puzzle of Andesite and Sandstone
The ruins of Puma Punku, part of the larger Tiwanaku archaeological site, are scattered with megalithic blocks that defy simple explanation. Radiocarbon dating of organic material suggests the complex was built by the Tiwanaku culture between 500 and 600 CE. The site is a collection of precisely shaped blocks made from two primary materials: red sandstone and grey andesite.
The largest stone block on site is a red sandstone slab measuring 7.81 meters long and 5.17 meters wide, with an estimated weight of 131 metric tons. Geochemical analysis shows this sandstone was transported from a quarry approximately 10 kilometers away, up a steep incline. The more complex carvings, including the famous H-blocks, are made from andesite, a volcanic rock with a hardness of 7 on the Mohs scale. This harder stone was sourced from quarries on the Copacabana Peninsula, about 90 kilometers away and across Lake Titicaca. The logistical challenge of transporting stones of this size and weight, at an altitude where no trees grow for use as wooden rollers, is part of the site's mystery.
Unexplained Engineering
The stonework at Puma Punku exhibits a level of precision that is difficult to account for with the tools believed to have been available to the Tiwanaku people. The culture relied on harder stone tools and abrasive materials like sand for construction. Yet, the H-blocks have flat faces, sharp 90-degree angles, and complex interlocking shapes. Many blocks were cut to interlock with such accuracy that a razor blade cannot fit between them. This precision suggests the possibility of prefabrication and mass production, as many blocks are uniform enough to be interchangeable.
The exact function of the H-blocks is unknown, but their interlocking design implies they were components of a larger structure, fitted together like a puzzle without mortar. Some blocks contain small, T-shaped cramp sockets, showing they were meant to be joined with metal fasteners. Analysis of remaining metal cramps revealed an unusual alloy of copper, arsenic, silicon, and nickel, a metal not found locally in Bolivia. Alternative theories propose that the blocks were not carved, but cast from a type of geopolymer concrete. Analysis of andesite samples has revealed the presence of organic matter, which is geologically impossible in volcanic rock, supporting the idea that the material was artificially created.