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

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 Ca_2.00(Mg_3.44Ti⁴⁺_1.49Fe_0.36Ti³⁺_0.34Al_0.24V³⁺_0.07Ca_0.06Cr_0.01)_⅀6.01(Al_3.63Si_2.37)_⅀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) ų, 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.