Three new iron-phosphate minerals from the El Ali iron meteorite, Somalia: Elaliite, Fe2+8Fe3+ (PO4)O8; elkinstantonite, Fe4(PO4)2O; and olsenite, KFe4(PO4)3

Abstract

Petrologic investigation of the El Ali IAB iron meteorite (Somalia) revealed three new minerals: elaliite (Fe2+8Fe3+ (PO4)O8, IMA 2022-087), elkinstantonite(Fe4(PO4)2O, IMA 2022-088), and olsenite (KFe4(PO4)3, IMA 2022-100). The name elaliite recognizes the occurrence of this mineral within the El Ali meteorite, originally located at 4° 17′ 17″N, 44° 53′ 54″E. Elkinstantonite is named after Linda (Lindy) Elkins-Tanton (b. 1965), a planetary scientist and professor in the School of Earth and Space Exploration at Arizona State University. The name olsenite is in honor of Edward J. Olsen (1927-2020), the former Curator of Mineralogy and Meteorites at the Field Museum of Natural History in Chicago (1960-1991). The new minerals and their names have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association. The holotype specimens of elaliite, elkinstantonite and olsenite consist of the polished block mount with accession number MET11814/2-1/EP1 deposited in the University of Alberta Meteorite Collection. Elaliite, elkinstantonite and olsenite occur along with wustite, troilite, sarcopside and Ca-bearing graftonite within inclusions in the iron-nickel metal (kamacite, 9.4 wt% Ni) that makes up the bulk of the El Ali sample. The empirical formulas determined by electron probe microanalysis for elaliite, elkinstantonite, and olsenite are: (Fe2+7.943Fe3+1.020Cr0.010Ni0.006Ca0.004Mn0.004)Σ8.987(P0.932Si0.077S0.005)Σ1.014O12, (Fe2+3.947Mn0.016Ni0.003Ca0.001Cr0.001)Σ3.968(P1.986Si0.014S0.013)Σ2.013O9, and (K0.820Na0.135Ca0.004)Σ0.959(Fe3.829Mn0.050)Σ3.879(P2.972S0.058Si0.017)Σ3.047O12. Electron backscatter diffraction was used to confirm the crystal structures of the three new minerals. Raman spectra for all three minerals are also presented.