Sometimes the most interesting thing to see in a rock is the parts that aren't rock: the voids in it. Geologists have hundreds of names for rocks and their textures and constituents; here are 11 names for the holes from druses to vugs. Some form by geological processes, others by living creatures—which is a geologic category of its own. These empty spaces are full of meaning. Drusy vug in a vesicle — Geology Guide photo
