Glossary

About Lime

• Argillaceous limestone is an impure type of limestone, containing considerable clay or shale, and, as a result, it has a relatively high silica and alumina content.
• Calcitic limestone is a term generally used by agronomists to convey a high calcium stone, but it could be misleading since its connotation might infer pure calcite, which it usually is not.
• Cement stone is an impure limestone, usually argillaceous, possessing the ideal balance of silica, alumina, and calcium carbonate needed for Portland cement manufacture.  When calcined it produces a hydraulic cementing material.
• Chalk is a soft, fine-grained, fossiliferous form of calcium carbonate, varying widely in colour, hardness, and purity.  White Chalk may be extremely pure, 98 to 99% calcium carbonate, whereas gray chalks may contain as much as 20% impurities.  The grain size is so minute that it was regarded as amorphous but is now considered to be cryptocrystalline.  The micro particles tend to be more rounded than octagonal, like calcite, and, as a result, have more surface area.
• Chemical-grade limestone is a pure type of high calcium or dolomitic limestone used by many of the chemical process industries or where exacting chemical requirements are necessary.  It contains a minimum of 95% total carbonate content.  (In a few areas of United States where an abundance of high-quality stone is available, the minimum may be 97 or 98% total carbonate.)
• Cherty limestone / siliceous limestone is an impure stone of unstable physical qualities, containing considerable silica.
• Dolomitic limestone contains considerable magnesium carbonate.  True, pure dolomitic stone contains a ratio of 40 to 44% MgCO₃ to 54 to 58% CaCO₃.  However, the term is more loosely used so that any carbonate rock containing 20% or more MgCO₃ is regarded as “dolomite.”  It varies in purity, hardness, and colour.
• Fluxstone is a pure form of limestone used as a flux or purifier in metallurgical furnaces.  It can be a high calcium, magnesium, or dolomitic type, providing the stone is low in impurities and contains at least 95% total carbonate content.  It is synonymous with metallurgical grade limestone.
• Glass stone is a pure form of high calcium or dolomitic stone, low in iron, used expressly for glass manufacture.  It qualifies as chemical grade stone.
• High calcium limestone is a general term for stone containing largely calcium carbonate and not much magnesium carbonate (only 2-5%, depending on one’s point of view).  It occurs in varying degrees of purity.
• Metallurgical grade limestone is the same as fluxstone.
• Whiting at one time connoted only a very finely pulverized, purified form of chalk, dust like CaCO₃ of micron sizes.  Now the term is used more broadly to include all finely divided, meticulously milled carbonates derived from high calcium or dolomitic limestone, marble, shell, or chemically precipitated CaCO₃.  Often it is referred to as “limestone whiting,” thus revealing its origin.  Unlike all of the preceding natural forms of limestone, it is strictly a manufactured product.