Citation: Teitler, Y.; Favier, S.; Ambrosi, J.-P.; Sevin, B.; Golfier, F.; Cathelineau, M. Evaluation of Sc Concentrations in Ni-Co Laterites Using Al as a Geochemical Proxy. Minerals 2022, 12, 615. https:// doi.org/10.3390/min12050615 Academic Editors: Cristina Domènech and Cristina Villanova-de-Benavent Received: 23 March 2022 Accepted: 10 May 2022 Published: 12 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). minerals Article Evaluation of Sc Concentrations in Ni-Co Laterites Using Al as a Geochemical Proxy Yoram Teitler 1, * , Sylvain Favier 1 , Jean-Paul Ambrosi 2 , Brice Sevin 3 , Fabrice Golfier 1 and Michel Cathelineau 1 1 Université de Lorraine, CNRS, GeoRessources, 54506 Vandoeuvre-lès-Nancy, France; sylvain.favier@univ-lorraine.fr (S.F.); fabrice.golfier@univ-lorraine.fr (F.G.); michel.cathelineau@univ-lorraine.fr (M.C.) 2 Aix-Marseille Université, CNRS, IRD, INRAE, CEREGE, CEDEX 4, 13545 Aix-en-Provence, France; ambrosi@cerege.fr 3 Service de la Géologie de Nouvelle-Calédonie, Direction de l’Industrie, des Mines et de l’Énergie, 1ter Rue Unger, BP 465, CEDEX, 98845 Nouméa, New Caledonia; brice.sevin@gmail.com * Correspondence: yoram.teitler@univ-lorraine.fr Abstract: Scandium (Sc) is used in several modern industrial applications. Recently, significant Sc concentrations (~100 ppm) were reported in some nickel-cobalt lateritic ores, where Sc may be valuably co-produced. However, Sc is typically not included in routine analyses of Ni-Co ores. This contribution examines the relevance of using routinely analysed elements as geochemical proxies for estimating Sc concentration and distribution. Three Ni-Co lateritic deposits from New Caledonia were investigated. In each deposit, Sc is well correlated with Al 2 O 3 . The slopes of deposit-scale Sc-Al 2 O 3 regression lines are remarkably controlled by the composition of enstatite from the parent peridotite. In all deposits, maximum Sc enrichment occurs in the yellow limonite, above the highest Ni and Co enrichment zones. Sc- and Al-bearing crystalline goethite is predominant in the oxide-rich zones, though Sc shows a higher affinity for amorphous iron oxides than Al. We propose that, in already assayed Ni-Co lateritic ores, the concentration and distribution of Sc can be estimated from that of Al. Deposit-scale Sc-Al 2 O 3 correlations may be determined after analysing a limited number of spatially and chemically representative samples. Therefore, mining operators may get a first-order evaluation of the Sc potential resource in Ni-Co lateritic deposits at low additional costs. Keywords: scandium; laterite; Ni-laterite; sequential extraction; New Caledonia 1. Introduction Scandium (Sc) is mainly used as a hardening additive to aluminium to form Al-Sc alloys for aerospace industries and high-quality sports equipment [1,2]. In addition, Sc is notably used in high-temperature lights, lasers, and ceramics manufacturing and finds promising applications in the development of Solid Oxide Fuel Cells (SOFCs). The global Sc supply and consumption remain marginal (~15 to 25 t/yr Sc 2 O 3 ,[3]). Sc is solely recovered as a by-product through titanium, zirconium, uranium, cobalt, and nickel process streams. Nevertheless, the development of energy-saving technologies and Sc extraction techniques have raised interest in this metal. In the last decade, Sc-rich occurrences with economically attractive grades and tonnages have been identified in some oxide-rich laterites developed after mafic and ultramafic rocks [4–14]. There, Sc enrichment is largely residual and results from the intense leaching of mobile cations during the lateritisation of the parent rock. Scandium is, thus, trapped and concentrated in neo-formed goethite, and moderate remobilisation can occur during repeated stages of goethite dissolution-recrystallisation and transformation into hematite. The chemical speciation of Sc in laterites from Australia and the Philippines has been investigated using a combination of X-ray absorption near- edge structure (XANES) spectroscopy and sequential extractions [7,8,11]. These studies Minerals 2022, 12, 615. https://doi.org/10.3390/min12050615 https://www.mdpi.com/journal/minerals