Winning streaks

Countless generations of geologists, pro and amateur alike, have sought the storied and striated agate. The philosopher and rockhound Theophrastus named it for the Achates, a river in Sicily where he presumably found his first fine specimen. Of course, when this pioneering prospector was combing the riverbanks around 300 BCE, these were already some seriously ancient stones. While their many dense silica layers make agates difficult to date, some earned their first stripes during the Archean Eon that ended 2.5 billion years ago. That means they're just about as old as life on Earth itself!