This sandstone from southern Nevada is part of the sediment veneer that covers the ancient metamorphic schists of the craton. The near-shore sandstone was in turn overlain by deeper-water limestone as a shallow sea encroached.
Coconino Sandstone. A small four-legged animal walked across a sand dune 265 million years ago, leaving behind its foot- and claw-prints. Before the tracks were erased, another sand layer covered and preserved them.
Fountain Formation, Pennsylvanian Period. Sandstone is a sedimentary rock--one that formed from sediments deposited at Earth's surface by water, ice, or wind. The sand and pebbles that make up this sandstone are fragments from older rocks. The fragments were carried downhill by rivers and streams 300 million years ago, deposited in layers, then bound together by natural cement.
The base of this sandstone baluster is missing its edges. They broke off along the layers under the weight of the sandstone itself and the stone railing the baluster supported. The circular marks were made by a saw when the piece was removed.
Carved brackets, Cretaceous Period. These two carved brackets were nearly identical when installed in the 1790s. Over the next 160 years, many layers of paint were applied to protect the easily weathered sandstone. The one with more paint retains more of the original detail.
Potomac Formation. A microscope photo of the sandstone reveals that it contains too much clay to be very durable. It also has other flaws (not visible here) that can cause big problems for a building stone: isolated large pebbles and clay lumps, and uncemented areas.
Turritella mortoni, Paleocene Epoch. What time is it? If you found this index fossil in a rock, you’d know. The animal was once widespread but quickly became extinct. Only a small percentage of fossils meet these criteria.