Ancient Chinese people may have used diamonds to polish their stone axes to mirrorlike finishes, according to a new analysis. Other than pushing back by several thousand years the date for the first known use of diamonds, the findings also suggest that Neolithic Chinese societies were more technologically advanced than previous studies had shown.
Some sections of the ax surfaces are almost as smooth as some silicon wafers used to make computer chips, says Peter Lu, a physicist at Harvard University. "Somehow, Stone Age people . . . were able to make something smooth enough that you could pattern a circuit on it," he says. In an attempt to discover how the polishing was done, Lu obtained four ceremonial burial axes from the tombs of two Neolithic