A、Rain water dissolves materials as it comes down a base of limestone or shale. B、People put dissolved materials into the soft w

The ground water can be divided into "soft water" and "hard water". Soft water has few impurities or none at all while hard water contains some more dissolved minerals. In general, hard water is drinkable, but it may have a slight taste because of various minerals.
    One place where hard water can be found is a ground underlying a base of limestone and shale. Rainwater dissolves materials as it comes down and this results in water’s taste and hardness.
    We can sometimes find ground water that is almost as soft as rainwater under a bare sandy area. These clays hard water from the underground is popular among the citizens of this country. They believe that mineral water is good for health, but some hard water has the dissolved minerals that are harmful to our body.
    Scientists suggest that all the ground water should be specially treated before, it is sold.