High-purity limestone assessment : from mine to market

High-purity limestone can be defined as carbonate rock that contains greater than 97% calcium carbonate (CaCO3, typically as calcite); it is often referred to as high-calcium or highly-calcitic limestone. Limestone has by far the largest number of commercial uses of all the industrial minerals; including construction (aggregate, cement and dimension stone), mineral fillers (for paper, paint, plastic, rubber and pharmaceuticals), adhesives, abrasives, fertilisers and soil conditioners, the production of cement, lime and calcium chemicals. Not all of these end-uses require high-purity limestone, especially the lower-value, bulk volume applications such as construction aggregate. However, this does not prevent high-purity limestone being used for these ‘lower-grade’ purposes. The strategic value of high-purity mineral resources is recognised by some national planning systems. In the UK, ‘Mineral Safeguarding Areas’ are designated as a means of preventing mineral resources becoming sterilised by other forms of development, preserving them for more appropriate end-uses and ensuring those developed have the least impact on the environment. Exploration for high-purity limestone involves more detailed examination of known deposits as defined by existing geological maps which may be accompanied by a limited amount of technical data. National geological surveys are usually responsible for reconnaissance-scale mineral resource assessments which have a national or regional focus and would consider a broad range of end-uses. The outcomes are disseminated as part of national mineral promotion. This would be followed by detailed resource assessments carried out by private companies looking to develop deposits for specific end-uses, such as cement production. Reconnaissance surveys often employ screening criteria to define the quality of the resources. The chief criterion for high purity limestone is the calcium carbonate content. The BGS employ the following definitions, based on calcium carbonate content (CaCO3): very-high purity (>98.5%), high purity (97-98.5%), medium-purity (93.5-97%), low-purity (85-93.5%) and impure (