Magnetism and archaeology: Magnetic oxides in the first American civilization

Abstract

Archaeological excavations at sites of the Olmec civilization (1500 to 500 B.C. in present-day Mexico) have unearthed artifacts formed from massive iron oxide ores. Iron oxide ores were ground and shaped into highly polished circular artifacts, called "mirrors", with flat and concave surfaces. These mirrors were employed as body adornments by societal elites and were involved in trade and commodity exchange over large distances. By means of 57Fe Mossbauer spectroscopy, the ore deposits from which material was obtained and the probable dissemination routes of the artifacts have been determined. An unusual bar-shaped artifact with a strong remanent magnetization suggests the existence of a device similar to a compass that predates the Chinese discovery by 103 years.