Calcium and other minerals in the water.
Any earth alkaline metal (2+)ion that will precipitate with carbonate ions. Eg. calcium, magnesium, iron and manganese ions.
It is caused by Calcium Hydrogen Carbonate :)
mgso4
Hardness of water pretains to the concentration of minerals and other trace elements in your local water supply. Well water-such in my area is "very hard"-meaning it contains a large amount of iron...
large waves destroying anything in its path