CALCIUM CARBONATE

Calcium carbonate (CaCO ₃) occurs naturally as calcite (density: 2.7), a widely distributed mineral. Calcite is a common constituent of sedimentary rocks, as a vein mineral, and as deposits from hot springs and in caves as stalactites and stalagmites. Calcite is white or colorless through shades of gray, red, yellow, green, blue, violet, brown, or even black when charged with impurities; streaked, white; transparent to opaque. It may occasionally show phosphorescence or fluorescence.

Calcium carbonate is one of several important inorganic chemicals (Fig. 1) and is widely used in both its pure and its impure states. As marble chips, it is sold in many sizes as a filler for artificial stone, for the neutralization of acids, and for chicken grit. Marble dust is employed in abrasives and in soaps. Crude, pulverized limestone is used in agriculture to sweeten soils, and pulverized arid levigated limestone is used to replace imported chalk and whiting.