Louisfuchsite, Ca2(Mg4Ti2)(Al4Si2)O20, a new rhönite-type mineral from the NWA 4964 CK meteorite: A refractory phase from the solar nebula

Abstract Louisfuchsite (IMA 2022-024), with an end-member formula Ca2(Mg4Ti2)(Al4Si2)O20, is a new refractory mineral identified in a Ca-Al-rich inclusion (CAI) from the NWA 4964 CK3.8 carbonaceous chondrite. Louisfuchsite occurs with spinel, perovskite, grossmanite, plus secondary rutile, titanite, and ilmenite in three regions in the CAI. The mean chemical composition of type louisfuchsite by electron probe microanalysis is (wt%) Al2O3 25.48, SiO2 18.40, MgO 17.92, TiO2 15.36, Ti2O3 3.13, CaO 14.92, FeO 3.30, V2O3 0.67, Cr2O3 0.08, total 99.26, giving rise to an empirical formula of Ca2.00(Mg3.44Ti4+1.49Fe0.36Ti3+0.34Al0.24V3+0.07Ca0.06Cr0.01)⅀6.01(Al3.63Si2.37)⅀6.00O20. Louisfuchsite has the P1 rhönite structure with a = 10.37(1) Å, b = 10.76(1) Å, c = 8.90(1) Å, α = 106.0(1)°, β = 96.0(1)°, γ = 124.7(1)°, V = 741(2) Å3, and Z = 2, as revealed by electron back-scatter diffraction. The calculated density using the measured composition is 3.44 g/cm3. Louisfuchsite is a new refractory phase from the solar nebula, crystallized from an 16O-rich (Δ17O ~ −24±2‰) refractory melt with the initial 26Al/27Al ratio of (5.01±0.24)×10−5 under reduced conditions. The mineral name is in honor of Louis Fuchs (1915–1991), a mineralogist at Argonne National Laboratory, for his many contributions to research on mineralogy of meteorites.