Calcium is the fifth element in abundance in the earth's crust, of which it forms more than 3%. It occurs as Limestone, Gypsum and Fluorite.
Calcium reacts with water to create an alkaline solution
2H2O Ca = Ca(OH)2 (calcium hydroxide) + H2
Calcium is found in drinking water where it adds to the hardness of the water. Calcium ions create scale in bathrooms and kitchens, and in appliances such as kettles.