Estimation of Nickel Laterite Resources and Reserves Using Ordinary Kriging and Inverse Distance Weighting (IDW) Methods: A Case Study from the Kolaka Block, PT Indrabakti Mustika, North Konawe Regency, Southeast Sulawesi

This study aims to assess the geological domains and estimate the nickel laterite resources and reserves within the Kolaka Block exploration area at PT Indrabakti Mustika, utilizing the Ordinary Kriging and Inverse Distance Weight (IDW) methods. The research employs quantitative and qualitative approaches to evaluate the geological framework and estimate the nickel laterite resources and reserves. Geological domain classification—limonite, saprolite, and bedrock layers—was achieved through detailed core section analysis, which informed the delineation of the nickel laterite zones. Based on the IDW method, the resource estimation results indicate 3,180,350 m³ (4,611,509 metric tons) of nickel laterite resources. This is subdivided into limonite zone resources (1,547,475 m³ or 2,243,840 metric tons) and saprolite zone resources (1,632,875 m³ or 2,367,669 metric tons). Using the Ordinary Kriging method, the total nickel laterite resource is estimated at 3,212,275 m³ (4,657,801 metric tons), with the limonite zone contributing 1,562,500 m³ (2,265,627 metric tons) and the saprolite zone contributing 1,649,775 m³ (2,392,174 metric tons). For the reserve estimation, the IDW method suggests a total of 1,205,875 m³ (1,748,520 metric tons) of nickel laterite reserves. These reserves are divided into limonite zone reserves (456,275 m³ or 661,600 metric tons) and saprolite zone reserves (749,600 m³ or 1,086,920 metric tons). In contrast, the Ordinary Kriging method estimates a total of 1,142,225 m³ (1,656,227 metric tons) of reserves, with limonite zone reserves of 516,700 m³ (749,216 metric tons) and saprolite zone reserves of 625,525 m³ (907,011 metric tons). These findings provide a comprehensive understanding of nickel laterite's geological and resource distribution in the Kolaka Block, offering crucial data for further exploration and development activities at PT Indrabakti Mustika.