Horváthite-(Y) mineral

Anhydrous sodium-yttrium fluorocarbonate mineral with current September 2026 IMA-CNMNC approved formula NaY(CO3)F2, status A, and approval number IMA 1996-032. Grice and Chao (1997) described the cotype specimen (CMNMI 81536, formerly provisional phase MSH UK-97) from a large irregular albitite-type pegmatite dike in the northeast wall of the Poudrette quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada, associated with albite, aegirine, dawsonite, rhodochrosite, Petersenite-(Ce), and Thomasclarkite-(Y). Electron-microprobe WDS analysis (mean of 2 analyses on 1 grain, p. 745) with CO2 calculated by stoichiometry yielded Na2O 12.62, CaO 1.86, Y2O3 45.07, Gd2O3 0.45, Tb2O3 0.12, Dy2O3 2.49, Ho2O3 0.81, Er2O3 3.02, Yb2O3 1.64, F 17.22, CO2 19.83 (calc), less O=F 7.23, total 97.90 wt%, corresponding on the basis of 1 C atom to the empirical formula (Na0.90Ca0.07)Sigma0.97(Y0.89Er0.04Dy0.03Yb0.02Gd0.01Ho0.01)Sigma1.00(CO3)F2.01 (low analytical total attributed by the authors to strong Na volatilization under a focused 5-um beam). Single-crystal X-ray diffraction refined in orthorhombic space group Pmcn (single-crystal cell a = 6.959(2), b = 9.170(2), c = 6.301(1) A, V = 402.1(2) A3, Table 2; powder XRD cell a = 6.964(3), b = 9.173(6), c = 6.302(2) A, V = 402.6(4) A3, Z = 4, R = 1.6%, Rw = 1.4% for 499 observed reflections with Fo > 5sigma(Fo) out of 555 unique reflections) revealed edge-sharing [YO4F4] square antiprisms and [NaO3F4] capped octahedra cross-linked by planar (CO3)2- groups. The mineral effervesces slowly in dilute HCl. Distinct from adamsite-(Y), thomasclarkite-(Y), shomiokite-(Y), and elemental yttrium; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.

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Record source: data/records/horvathite-y.yaml