Petrology and Geochemistry of Scandium in Wailukum Ni Laterites, East Halmahera, Indonesia

The Wailukum area in North Maluku Province, Indonesia, is an ultramafic rock com-plex with a high degree of serpentinization. The mineral composition of ultramafic and mafic rocks strongly influences scandium (Sc) distribution and enrichment during lat-eritization. This study aims to analyze the element distribution, mineral composition, and rock identification in three types of geological materials in a lateritic profile which contains Sc, specifically bedrock, saprolite, and limonite. The analytical methods used are petrography, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Inductively Cou-pled Plasma (ICP), and Scanning Electron Microscopy – Energy Dispersive Spectros-copy (SEM-EDS). Results show that in the bedrock, Sc is mainly hosted in clinopyrox-ene minerals such as augite and diopside, with minor amounts in chromite, magnetite, dolomite, and anorthite. In the saprolite, Sc content decreases due to higher mobility but remains partly associated with clinopyroxene and chromite. In the limonite zone, Sc reaches maximum enrichment, primarily hosted in Fe–Mn oxides including goe-thite, magnetite, and asbolane. Among rock types, gabbro contains the highest abso-lute Sc concentration (23.25 ppm in bedrock and up to 58.5 ppm in limonite), while wehrlite records the greatest enrichment ratio, with a 9.18-fold increase from bedrock to limonite. In contrast, gabbro shows the lowest enrichment ratio (2.52-fold) despite its high initial Sc content. These patterns indicate that Sc enrichment is controlled by clinopyroxene as the primary host in bedrock, its relative stability during weathering, and the subsequent fixation of Sc in Fe, Cr, and Mn oxides within the lateritization profile.