Have you tried to clean the calcium deposits on toilets and sinks using the pumice stone? It is not easy and more often than not it leaves scratch marks. And using harsh chemicals is not only hard on the skin but also on the nose and sinuses.
I know a easy trick that doesn’t take alot of elbow grease or time….using something that can be cheaply bought at either Walmart or any hardware store. It is drywall sandpaper. Not the kind that looks like regular sandpaper but the one that has holes with a lattice design. I cut these in 1″ strips which are easy to hold. Amazingly enough all you have to do is rub the calcium stain with the sandpaper strip and it almost always removes the calcium. The sandpaper does not scratch the ceramic. It is sometimes easier to clean if you remove the water from the toilet. Which can be done with a toilet plunger, by forcing the water down the drain. I then rub off the calcium and flush. Sometimes you need to flush and rescrub a couple of times before it is all gone. But it is a lot easier that any other method I have tried. It also works on sinks, tubs and showers that are made out of ceramic. Though be careful around the faucets and other metal parts as those will scratch. The sandpaper will remove stains that you didn’t think could be cleaned.