I set my 8 year old to work with a rubber mallet and old screwdriver on a landscape boulder in a SE Seattle neighborhood where the bedrock is the Blakeley formation, and where the homeowner was pretty sure their boulders were local bedrock. This was his favorite find, I said it looks like a bit of leaf/seed pod/wood to me. Anyone have thoughts about what it is? It measures almost exactly 1.0 cm x 0.5 cm.