typhlonectes:Sandstone Concretion The large sandstone concretion welcomes guests to the Morian Hall
typhlonectes:Sandstone Concretion The large sandstone concretion welcomes guests to the Morian Hall of Paleontology overlook. These large concretions are formed naturally when super heated water flowed through billions of tiny grains of fine quartz sand. (via: Houston Museum of Natural Science) -- source link