|Calcium is a alkaline earth metal, and is the fifth most abundant element by mass in the Earth’s crust. It is essential for living organisms, particularly in cell physiology, where movement of the calcium ion Ca2+ into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used in mineralization of bones and shells, calcium is the most abundant metal by mass in many animals. It is uesd as a reducing agent in the extraction of other metals, such as uranium, zirconium, and thorium, as a deoxidizer, desulfurizer, or decarbonizer for various ferrous and nonferrous alloys, and as an alloying agent used in the production of aluminium, beryllium, copper, lead, and magnesium alloys. It is also used in the making of cements and mortars to be used in construction and in the making of cheese, where calcium ions influence the activity of rennin in bringing about the coagulation of milk.
Calcium producers/suppliers – http://www.worldofchemicals.com/chemicals/manufacturers/fl/calcium.html