Crude or roughly broken limestone typically falls under HTS Chapter 25, while calcined lime (quicklime or hydrated lime) moves to Chapter 28 as a chemical product. The degree of processing and the CaCO₃ purity level are both relevant to classification, and importers should confirm the correct heading with a licensed customs broker to avoid misclassification between mineral and chemical chapters.

Steel manufacturing (flux-grade limestone), water treatment (hydrated lime), chemical production (high-purity calcium carbonate), and environmental compliance applications (flue-gas desulfurization) are the primary industrial consumers. Agricultural lime demand is largely met domestically due to the commodity's low value-to-weight ratio, making long-haul imports economically marginal for that grade.