Lime and Limestone are often confused terms. It is not unusual that users will refer to limestone as lime and less often to lime as limestone.

Limestone is a term that embraces carbonate rocks composed primarily of calcium carbonate or combinations of calcium and magnesium carbonate with the most common impurities being silica and alumina.

Lime derived from limestone is the product of calcined limestone generally referred to as quicklime or hydrated lime. The calcination process involves the heating of limestone in order to expel the carbon dioxide from the stone to form calcium oxide (quicklime), and then hydrated (slaked) lime can be created by the addition of water. The two products are quite different, though the term ‘lime’ is used to describe them both.

Lime and limestone are among the oldest materials used by mankind. The most recognisable use of these two as construction materials is the use by the Egyptians in the construction of the Pyramids. They used both limestone blocks and lime and gypsum mortar and plaster between 4,000 and 2,000 B.C. The Greeks and Romans record the use of lime as a bleaching agent as far back as 350 B.C. and for its medicinal properties from 75 A.D. The long history of the Romans using both limestone and lime in the construction of great highways is well documented and the list goes on and on.

It is speculated that the earliest recognition of the occurrence of lime was the result of slabs of limestone used by primitive man to contain his fires disintegrating into a white, paste-like putty following rain. The limestone calcined by the heat of his fire, and the resulting quicklime then hydrated by the rain. The technology of calcining limestone to produce lime has progressed significantly to the point where today there is a range of kilns available to suit a variety of limestone to be calcined and the fuels available to fire them.