Manganoarrojadite-(KNa), KNa5MnFe13Al(PO4)11(PO3OH)(OH)2, a new arrojadite-group mineral from the Palermo No. 1 mine, New Hampshire, USA. (11th December 2020)

• Record Type: Journal Article
• Authors: Lykova, Inna; Rowe, Ralph; Poirier, Glenn; Helwig, Kate; Friis, Henrik
• Is Part Of: Mineralogical magazine. Volume 84:Number 6(2020)
• Page Start: 932
• Page End: 940
• Publication Date: 2020-12-11
• Subjects: manganoarrojadite-(KNa), -- new mineral, -- arrojadite group, -- crystal structure, -- pegmatite, -- Palermo No. 1 mine, -- USA; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/mgm.2020.88
• Languages: English
• ISSNs: 0026-461X

Abstract

Abstract: A new arrojadite-group mineral manganoarrojadite-(KNa), ideally KNa5 MnFe13 Al(PO4 )11 (PO3 OH)(OH)2, was found in a phosphate-bearing granite pegmatite at the Palermo No. 1 mine, New Hampshire, USA. It forms anhedral grains up to 1 × 1.5 cm in size combined in aggregates with vivianite, goyazite, quartz and calcite. The mineral is olive green with a pale green streak and vitreous to greasy lustre. The cleavage is good in one direction. The Mohs hardness is 4½. D calc is 3.53 g/cm 3 . Manganoarrojadite-(KNa) is optically biaxial (–), α = 1.658(2), β = 1.666(2), γ = 1.670(2), 2Vmeas. = 67(1)° and 2Vcalc. = 70° (589 nm). The infrared spectrum is reported. The composition (wt.%) is Na2 O 6.97, K2 O 1.78, CaO 0.31, MgO 2.17, MnO 12.30, FeO 31.17, Al2 O3 2.43, P2 O5 40.48, F 0.30, H2 O 1.32, O = F2 –0.13, total 99.10. The empirical formula calculated on the basis of 12 P and (O+OH+F) = 50 apfu is Na4.73 K0.80 Ca0.12 Mg1.13 Mn 2+ 3.65 Fe 2+ 9.13 Al1.00 P12.00 O46.59 OH3.08 F0.33 . The ideal structural formula is A 1 K A 2 Na B 1 Na B 2 Na Na1, 2 Na2 Na3 □ C Mn M Fe13 Al(PO4 )11 (PO3 OH) W (OH)2 . The mineral is monoclinic, Cc, a = 16.5345(3), b = 10.0406(2), c = 24.6261(5) Å, β = 105.891(2)°, V = 3932.09(14) Å 3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [ d, Å( I )( hkl )] are: 5.902(24)(202), 5.025(24)(020), 3.208(47)(206, $\;\bar{1}$ 32), 3.048(100)( $\bar{5}$ 14, $\bar{4}$ 24), 2.758(24)( $\bar{6}$ 02) and 2.704(70)(226). The crystal structure, refined from single-crystal X-ray diffraction data ( R 1 = 0.025), is of the arrojadite structure type. Manganoarrojadite-(KNa) is the first arrojadite-group mineral with Mn dominant on the site usually occupied by Ca and without Ca as the dominant cation at any cation site.