I've polished things with sand before and used hammerstones, yes. I'm not a stonemason though, just somone who spent a lot of time as a kid playing with rocks.
Most people will have some familiarity with emery cloth/sandpaper, which are basically the same principle. We don't even need to look at fancy egyptian statues. Carnelian beads were a common trade item across the Ancient near east and Egypt made this way. It's not magic.