A lump of lime heated in a flame of hydrogen and oxygen glows a brilliant white, and before electric light this was the limelight of the Victorian stage. Lime mortar is the oldest cement: slaked with water to calcium hydroxide and mixed with sand, it sets by taking carbon dioxide back from the air and turning into calcite again, closing the circle it started from. The crystal has the same chessboard structure as halite.
Research Elements Compound · CaO One unit cell, the smallest block that repeats in every direction to build the whole crystal. Atoms on its faces, edges and corners are shared with the neighboring cells. Farther atoms are drawn fainter. Atom positions from the Crystallography Open Database entry 9006694 (Fiquet, G.; Richet, P.; Montagnac, G., 1999). Almost never as a mineral, because it takes up water and carbon dioxide from the air within days and turns back into calcium hydroxide and calcite. It has been found in limestone baked by lava at Vesuvius and in the ash of burning coal seams. Nearly all the lime in the world is made, not found. Not mined but burned: limestone (calcite) is quarried, crushed to lumps and heated to 900 to 1,100 °C in vertical shaft kilns or long rotary kilns, which drives off the carbon dioxide and leaves quicklime. Steelmaking takes the largest share, as a flux that pulls silica, phosphorus and sulfur out of the molten iron. The rest goes to water treatment, flue-gas scrubbing, sugar refining, soil and mortar.Lime
Elements
Crystal structure
Cell: a = b = c = 4.815 Å, all angles 90°
Space group: F m -3 mWhere it's found
How it's mined
Notes