Clay concretions are known by several names like clay babies, clay dogs and fairy stones. WAMS-Olympia received several of these concretions as part of a rock donation in the summer of 2024. Their origin is unknown, but most likely they were collected on beaches near Fox Island.
Clay babies formed in the quite pure beds of clay that were deposted during the last glacial period in Puget Sound. 17,000 to 18,000 years ago a lobe of the Vashon Glacier blocked streams, rivers and melt water that normally would flow North and out of Puget Sound. In this “proglacial lake” clay, mud and silt built up season after season. Stone-like concretions formed then eroded out of the clay beds during present day conditions.
Jim Sachet gave a Rock Talk on Clay Babies during our November 5th club meeting. Take a look at the attached presentation!