Fossilized Devonian Sea Sponge This specimen is a fossilized sponge or "Demospongiae" from the Devonian period- about 400-450 million years ago. It is light like a pumice stone and filled with little crystalized structures that sparkle in the sunlight. I found it in central/eastern Iowa with other Devonian fossils, though this is the first of its kind for me. One of my coolest fossil finds! Kept in a smoke-free home. #fossil #geology #rocks #crystals #quartz