Anyone who makes pasta a lot has probably seen this happen. Doesn't have to be distilled water, though it works better with pure water. A great deal of it has to do with the boiling method. Since a microwave evenly and gently heats the water, it will happen easier in there. Most people agitate water that's on the stove and don't use distilled water to boil food.
As a physics experiment, it's pretty cool. Blind, don't let me have to get an earful from one of your parents because you decided to try this at home.
On the original topic, lots of bottled water has minerals added. I'd run it through a complete chlorine, iron, phosphate, silicate, nitrate, etc, etc test before considering using it. I assume most bottled water doesn't have fluoride in it.