The term Calcium is based on the Latin words "calx" and "calcis," meaning "lime." The ancient Romans were known to make lime from limestone or calcium carbonate, a naturally occurring compound found in Earth's crust.
Calcium is the fifth most abundant element in the Earth's crust, comprising 3.5 percent of its total volume. Calcium can be found in a number of naturally occurring compounds such as chalk, marble and gypsum. Roman concrete was invented by mixing lime with volcanic ash and rock. The Roman Colosseum is one example of what can be made with the many forms of Calcium that exist.