A rock is usually a symbol of deep time. Kick a pebble or toss a stone and you’ve probably just touched something that formed before humans walked upright. Some stones, however, are a unmistakable, and beautiful, product of human history.Before car factories were fully automated, workers sprayed vehicles with paint by hand. It was a messy process. And over time, misses and thick coats would drip from the cars and pool where the cars went to dry. As the cars baked, so did the paint runoff. The drier was a stand in for the oppressive temperatures and pressures of the Earth’s inner layers, and soon the pooled paint was rock-solid. When factory workers eventually cleaned the painting stations, this synthetic lasagna of paint broke apart to reveal beautiful, layered “stones” that could be polished to a fine shine. Named after the places it was made, “Fordite,” or “Detroit agate,” was born.

The different layers of paint tell a story — car color trends can be traced back in time, as can the occasional metallic sparkle of a boat.

Factory workers, admiring the fordite themselves, likely took the man-made stones home to their families. Pieces of fordite soon found their way into gem shops and artist hands — today you can buy fordite jewelry as easily as you can gemstone. But our supply of fordite, unlike stones forming beneath our feet, will never be replenished. Most modern car factories now use a painting process that effectively eliminates the runoff that previously formed the foundation of fordite. The creation is a relic, a signpost of pollution and waste. At least it’s a beautiful one.–IMAGES: MininGeology; Fordite.com