Parafiniukite, Ca₂Mn₃(PO₄)₃Cl, a New Member of the Apatite Supergroup from the Szklary Pegmatite, Lower Silesia, Poland: Description and Crystal Structure

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.

Keywords

• parafiniukite
• apatite supergroup
• hedyphane group
• manganese
• calcium
• phosphorus
• Szklary pegmatite
• Lower Silesia
• Poland