It occurs commonly in sedimentary rocks in the minerals Calcite, Dolomite & Gypsum. It also occurs in Igneous and metamorphic rocks – chiefly in the Silicate minerals: Plagioclasses, Amphiboles, Pyroxenes and Garnets.
It is a soft gray alkaline earth metal, 5th most abundant element by mass in the Earth’s crust. It is the 5th most abundant element dissolved ion in seawater by molarity and mass, after Sodium, Chloride, Magnesium and Sulfate.
Free Calcium metal is too reactive to occur in nature.
Calcium is reactive and soft for a metal, though harder than lead, it can be cut with a knife with difficulty.
It is extracted by electrolysis from a fused salt like Calcium Chloride.
In powdered form, the reaction with water is extremely rapid.
Calcium is the lightest of the alkaline earth metals; Magnesium and Beryllium are denser though lighter in atomic mass. From Strontium onward, alkali earth metals become denser with increasing atomic mass.
Calcium has a higher electrical resistivity than Copper or Aluminium, yet weight-for-weight, due to its much lower density, it is a better conductor.
Calcium, combined with phosphate, forming Hydroxy Lapatite, is the mineral portion of human and animal bones and teeth.
CHALK, Marble, and Limestone are all forms of Calcium Carbonate.
