Calcium minerals occur throughout the world in the greatest profusion, the most familiar examples being the various forms of carbonate (chalk, coral, limestone, marble, and magnesium limestone or dolomite), and the sulphates (gypsum and anhydrite). Davy prepared metallic calcium as a powder by electrolysing calcium chloride in presence of mercury, and heating the resultant amalgam. Matthiessen obtained it in a compact form by melting a mixture of 2 molecules calcium chloride and 1 of strontium chloride (with a little sal-ammoniac to facilitate the fusion) in a porcelain crucible, containing a carbon positive pole, and provided with a negative pole in the form of a thin harpsichord wire wound upon a stouter wire, and only just entering the liquid mixture. Beads of the reduced metal attach themselves to the fine wire. Lies Bodart reduces the metal by fusing a mixture of 1 part sodium with 7 of fused calcium iodide in a closed iron crucible, commencing with a dull-red and advancing to a bright-red heat. Caron fuses 3 parts fused powdered calcium chloride, 4 of fairly granulated distilled zinc, and 1 of sodium in small pieces, in a crucible heated to redness in an ordinary furnace. The action is feeble at first. When zinc flames begin to arise, the heat is moderated to check volatilization.
After about 15 minutes in this state, the crucible may be withdrawn, and, on cooling, a metallic button will be found at the bottom. This alloy of calcium and zinc, containing 10 to 15 Per cent. of the former, is placed in a gas-carbon crucible and heated till all the zino is disengaged. Calcium has a sp. gr. of 1.5778; it is malleable, tenacious, harder than lead, and of a yellow colour; it oxidizes rapidly in moist air, but slowly in quite drv.