Artifact
Gregory Benford
A team of archeologists in Greece uncover what proves to be a progressively more complicated riddle: A big black limestone rock with a single amber horn in it. This artifact bears no resemblance to any other Macedonian artifact found and causes even further trouble by being discovered right in the middle of a Greek coup d'etat.
Do not read the afterward before you read the story, as it contains lots of explanation of the science behind the artifact and that's just one spoiler after another if you haven't read the body of the book yet.
