Unusual Properties: This very strange sandstone is made up of loosely joined silicon grains which give it the consistency of loosely joined jig-saw puzzle pieces. As a result it is the only rock known that can actually bend! As shown by the photographs below. This is actually a sedimentary sandstone that was formed at the bottom of an ocean many millions of years ago. The sand that was deposited by rivers into the ocean had a lot of silicon nodules. These fused together over a long period of time and at great pressure and heat, until they formed this sandstone rock. However, the bonding between the silicon nodules is much like a jig saw puzzle where the pieces do not fit very tight. This allows the pieces to have a lot of play and be loosely bound to each other. Same thing applies here. The silicon nodules are loosely linked together, allowing the rock to actually bend due to the loose connections between the particles of sand that created the sandstone.