Moisten a sponge with water. Sprinkle baking soda over one side of the damp sponge.
Scrub the calcium spots on your natural stone shower. Rinse the sponge as needed. Add more baking soda and continue to clean the stones to loosen and remove as much of the calcium deposits as possible.
Fill a bucket with 1 gallon of warm water. Pour 1 cup of ammonia into the bucket of water.
Dampen a cloth with the diluted ammonia solution. Use it to wash off any remaining calcium spots on your natural stone shower.
Rinse your shower with water. Dry the natural stone surface with clean cloths.