How is Calcium Made?
Calcium, a vital element for human health and found abundantly in the Earth's crust, originates from two primary sources: stellar nucleosynthesis and industrial processes.
The vast majority of calcium in the universe, including that in our bodies, originated in stars. Specifically, exploding stars, or supernovas, are responsible for scattering massive quantities of this essential mineral across the cosmos. 1 These powerful events forge elements heavier than iron, including calcium, which then becomes incorporated into celestial bodies, ultimately forming the basis of our planet's calcium reserves.
Industrial Production: Extracting Calcium on Earth
While the initial source of calcium is celestial, humans extract it for practical uses through industrial processes. Two main methods are employed:
1. Electrolysis of Calcium Chloride:
Calcium metal can be produced commercially through the electrolysis of a fused salt, such as calcium chloride. This method involves passing an electric current through molten calcium chloride, causing the calcium ions to be reduced and deposited as elemental calcium. However, once exposed to air, the calcium rapidly reacts to form a coating of grey-white calcium oxide and nitride. 2
2. Heating Lime with Aluminum:
A more modern industrial method involves heating lime (calcium oxide) with aluminum in a vacuum. This process yields pure calcium metal. This approach has largely replaced the electrolysis method as the preferred commercial method for producing pure calcium. 3 4
Calcium Compounds in Nature
While the methods above refer to the production of elemental calcium, it's crucial to understand that most calcium found in nature exists within compounds. The most abundant calcium compound is calcium carbonate, which makes up limestone and the fossilized remains of ancient marine life. Other naturally occurring calcium compounds include gypsum, anhydrite, and fluorite. 5 These compounds contribute significantly to the Earth's geology and serve as sources for industrial calcium extraction.
Examples of Calcium in Nature:
