Sandstone is a natural stone that distributors quarry for use in and around dwellings. Masonry builders believe sandstone to be a soft stone, which makes drilling into deposits easier than drilling into hard stones like granite or marble. However, since sandstone is a sedimentary rock, it can contain holes from ancient organisms (such as coral) or even fossils (like brontosaurus bones). Even if the hole appears empty, there may be moisture inside the rock that could expand and cause the wood to rot. The good news is that sandstone is relatively easy to cut with an abrasive tool such as a power sander or orbital sander. You will probably need to do some experimenting to find the right speed and pressure for your sander. Use a finer grit sandpaper first to remove any residual material from the hole before drilling deeper into the stone. Once you have drilled all the way through the stone, stop when you hit water. This is because water-filled cracks and holes in sandstone are called "faults" and they can lead down deep within the stone where you don't want them to go. Faults are usually not serious problems but if you get water in areas of the house that aren't supposed to be wet, you might have to repair the stone surface to keep out future leaks.