Rock surfaces carry messages from ancient times. 

A stone picked up on a mountain slope and held in one’s hand may have formed in the Paleogene, some fifty million years ago, or in the Paleozoic – five hundred million. It may have been baked during ages of global warming and frozen under glaciers weight. Who knows what forces shaped its surface. Geologists are experts at reading these messages by analyzing the mineral composition of rocks. 

Yet even without extracting such information, patterns on rock surfaces are sometimes beautiful and astonishing.