Hidden wealth in Puttalam Aruwakkalu limestone deposit By Arundathie Abeysinghe
The Aruwakkalu limestone deposit, a part of the Jaffna limestone located 25 kilometers north of Puttalam in Northwestern Province (recognised as the backbone of Sri Lanka’s cement industry), mainly operated by Siam City Cement (Lanka) Limited (INSEE Cement) to feed its Puttalam manufacturing plant is currently undergoing a significant strategic transformation towards a more sophisticated, multi-resource extraction model, thus separating valuable mineral sands such as Ilmenite, Rutile, and Zircon from the topsoil layer. This strategy represents a significant divergence from the long-standing approach that viewed the topsoil as merely a waste product.
Aruwakkalu is also the location of Sri Lanka’s largest open-cast limestone mine that provides the primary raw material for Sri Lanka’s cement industry.
According to senior officials of the Ministry of Industries, “although, for several decades, the Miocene limestone has been the primary focus for industrial excavation, the government has recently turned towards a more sophisticated, multi-resource extraction model. This transformation has recently been cemented by the adoption of a groundbreaking proposal by the Cabinet of Ministers that requires the submission of Expressions of Interest (EOI) to separate valuable mineral sands such as Ilmenite, Rutile, and Zircon from the topsoil layer. This newly adopted strategy signifies a major divergence from the long-standing approach which viewed the topsoil as a waste product. Hence, under the guidelines of the National Mineral Policy 2026, the government has adopted the principle of “value addition” through investments with the objective of increasing export revenue, while strictly enforcing environmental as well as social safeguards.”
According to senior officials of the Geological Survey and Mines Bureau (GSMB) “a system will be put in place to ensure that all particles of Ilmenite and Rutile are accounted for within a transparent and competitive manner where national interests come first. GSMB is the sole institution authorised to issue exploration, mining, trading licenses and transport, including monitoring the Industrial Mining Licenses (IML). GSMB also conducts systematic core drilling and mineral surveys to assess the commercial viability of deposits, such as the limestone and mineral sands at Aruwakkalu.”
Geologists Thushari de Mel and Asantha Kumrapperuma are of the view that “the limestone deposit is part of the extensive Miocene-era (major geological period spanning from 23 to 5.3 million years ago) Jaffna limestone belt in Northern Province (mostly made up of calcarenite). The deposit comprises an excess of red soil and low-grade limestone that forms the base of a high-grade limestone layer which extends below sea level.”
“Aruwakkalu limestone deposit is a significant resource for the cement industry as well as a globally recognized geological and paleontological treasure. Its scientific importance lies in its rich Burdigalian Age (approximately 20.4 to 15.9 million years ago) fossil record that provides crucial clues for dating regional Jaffna limestone and understanding ancient marine ecosystems. The site comprises a rich fossil record of marine invertebrates and vertebrates which offer crucial insight into the ancient marine ecosystems of the Indian Ocean,” Thushari and Asantha emphasized.
According to senior academics Sampath Amarasekera and Mandana Kaluwitharana “Aruwakkalu limestone deposit has a geological and scientific importance as its Miocene fossil beds that include well-preserved giant oysters as well as gastropods. These geological features are immensely valuable for paleontological research and dating. As the presence of the index foraminifer Pseudotaberina malabarica, an index fossil of the Burdigalian Age and other fossils that are significant for scientists to accurately date marine sequences in South Asia as the stratigraphic layers at the site are immensely packed with fossils of corals, gastropods, bryozoans and giant oysters which indicates that the region was covered by shallow, warm, and nutrient-rich tropical waters previously.”
