Squashed in a rock

Fifty million years ago, a giant salt lake existed in northwestern Colorado. Leaves, feather-like seeds (upper right, above), and a diverse array of insects, such as the lacewing shown above, fell into the lake. Over the millennia, the tissues of these organisms became mineralized—only to be later dissolved away by groundwater. Now all that remain are the bleached outlines of where the minerals used to be. Truly a ghost of a fossil!