IMA 2018-047 = parafiniukite

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Marco E. Ciriotti
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IMA 2018-047 = parafiniukite

Messaggio da Marco E. Ciriotti » ven 26 ott, 2018 13:44

Referenza:
▪ Pieczka, A., Biagioni, C., Gołębiowska, B., Jeleń, P., Pasero, M., Sitarz, M. (2018): Parafiniukite, Ca2Mn3(PO4)3Cl, a New Member of the Apatite Supergroup from the Szklary Pegmatite, Lower Silesia, Poland: Description and Crystal Structure. Minerals, 8, 485; https://doi.org/10.3390/min8110485.

Abstract:
Parafiniukite, ideally Ca2Mn3(PO4)3Cl, is a new apatite-supergroup mineral from the Szklary pegmatite, Lower Silesia, Poland. It occurs as anhedral grains, up to 250 µm in size, dark olive green in colour, embedded in a mixture of Mn-oxides and smectites around beusite. It has a vitreous luster, and it is brittle with irregular, uneven fracture. The calculated density is 3.614 g·cm−3. Parafiniukite is hexagonal, space group P63/m, with unit-cell parameters a = 9.4900(6), c = 6.4777(5) Å, V = 505.22(5) Å3, Z = 2. The eight strongest reflections in the calculated X-ray powder diffraction pattern of parafiniukite are [d in Å (I) hkl]: 3.239 (39) 002; 2.801 (55) 211; 2.801 (76) 121; 2.740 (100) 300; 2.675 (50) 112; 2.544 (69) 202; 1.914 (31) 222; and 1.864 (22) 132. Chemical analysis by an electron microprobe gave (in wt%) P2O5 39.20, MgO 0.19, CaO 24.14, MnO 31.19, FeO 2.95, Na2O 0.05, F 0.39, Cl 3.13, H2O(calc) 0.68, O=(Cl,F) −0.87, sum 101.05. The resulting empirical formula on the basis of 13 anions per formula unit is (Mn2.39Ca2.34Fe0.22Mg0.03Na0.01)Σ4.99P3.00O12[Cl0.48(OH)0.41F0.11]. The crystal structure of parafiniukite was refined to an R1 = 0.0463 for 320 independent reflections with Fo > 4σ(Fo) and 41 refined parameters. Parafiniukite is isotypic with apatites. Manganese is the dominant cation at the M(2) site, and Ca is the dominant cation at the M(1) site.
Marco E. Ciriotti

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