The Living Drill Bits That Grind Holes in Beach Rocks
Perhaps you’ve seen them strewn along the seashore: a smooth, round pebble with a perfect hole right through it, or a chunk of shale with several holes neatly arranged in suspiciously consistent rows.
“It strikes people’s curiosity,” says Rebecca Johnson, codirector of the Center for Biodiversity and Community Science at the California Academy of Sciences. “It’s really common along our beaches to see these hole-filled rocks and be really confused about what possibly could have made this hole.”
People from the British Isles have long called these uncanny rocks hagstones, holey stones, or witch stones. Some people believe the stones grant magical powers: sailors tie hagstones to the sides of their ships to ward off bad weather and witchcraft. Other traditions included hanging hagstones above beds to repel nightmares or in stables to protect horses, or wearing hagstone necklaces as protective talismans.
But what made these captivating stones in the first place?