Here’s a super simple tip that can help you with a vexing problem. Natural stone shower walls tend to be straightforward to clean but sometimes the stone has a rough surface so that any sponge or cloth that you use on it will get torn to shreds. So instead of standing there scratching your head and saving it for another day, here’s an easy solution: use a scrub brush! And use a good, nontoxic stone cleaner while you’re at it (and lots of water). I use Simple Green Stone Cleaner, available at hardware stores.