Underwater caves in Mexico preserve one of the world’s oldest ochre mines (Science 07/03/20)
Crouching as she wound her way through a pinched underground corridor, a young woman grasped a torch in one hand, soot blackening the craggy ceiling above her. Guided by stacks of stones deeper and deeper in the darkness of the cave, she finally spied her prize: a blood-red vein of rock in the fire-lit wall.…