Manganoarrojadite-(KNa), KNa (sub 5) MnFe (sub 13) Al(PO (sub 4) ) (sub 11) (PO (sub 3) OH)(OH) (sub 2) , a new arrojadite-group mineral from the Palermo No. 1 Mine, New Hampshire, USA
Manganoarrojadite-(KNa), KNa (sub 5) MnFe (sub 13) Al(PO (sub 4) ) (sub 11) (PO (sub 3) OH)(OH) (sub 2) , a new arrojadite-group mineral from the Palermo No. 1 Mine, New Hampshire, USA
Mineralogical Magazine (December 2020) 84 (6): 932-940
- alkali metals
- calcite
- carbonates
- chemical composition
- coexisting minerals
- crystal structure
- formula
- framework silicates
- goyazite
- Grafton County New Hampshire
- granites
- igneous rocks
- infrared spectra
- metals
- New England
- New Hampshire
- new minerals
- pegmatite
- phosphates
- plutonic rocks
- potassium
- quartz
- silica minerals
- silicates
- sodium
- space groups
- spectra
- unit cell
- United States
- vivianite
- X-ray diffraction data
- arrojadite
- Palermo Mine
- manganoarrojadite
A new arrojadite-group mineral manganoarrojadite-(KNa), ideally KNa (sub 5) MnFe (sub 13) Al(PO (sub 4) ) (sub 11) (PO (sub 3) OH)(OH) (sub 2) , was found in a phosphate-bearing granite pegmatite at the Palermo No. 1 mine, New Hampshire, USA. It forms anhedral grains up to 1X1.5 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 4 and 1/2. D (sub calc) is 3.53 g/cm (super 3) . Manganoarrojadite-(KNa) is optically biaxial (-), alpha =1.658(2), beta =1.666(2), gamma = 1.670(2), 2V (sub meas.) =67(1) degrees and 2V (sub calc.) =70 degrees (589 nm). The infrared spectrum is reported. The composition (wt.%) is Na (sub 2) O 6.97, K (sub 2) O 1.78, CaO 0.31, MgO 2.17, MnO 12.30, FeO 31.17, Al (sub 2) O (sub 3) 2.43, P (sub 2) O (sub 5) 40.48, F 0.30, H (sub 2) O 1.32, O=F (sub 2) -0.13, total 99.10. The empirical formula calculated on the basis of 12 P and (O+OH+F)=50 apfu is Na (sub 4.73) K (sub 0.80) Ca (sub 0.12) Mg (sub 1.13) Mn (super 2+) (sub 3.65) Fe (super 2+) (sub 9.13) Al (sub 1.00) P (sub 12.00) O (sub 46.59) OH (sub 3.08) F (sub 0.33) . The ideal structural formula is (super A1) K (super A2) Na (super B1) Na (super B2) Na (super Na1,2) Na (sub 2) (super Na3) [] (super C) Mn (super M) Fe (sub 13) Al(PO (sub 4) ) (sub 11) (PO (sub 3) OH) (super W) (OH) (sub 2) . The mineral is monoclinic, Cc, a=16.5345(3), b=10.0406(2), c=24.6261(5) Aa, beta =105.891(2) degrees , V=3932.09(14) Aa (super 3) and Z=4. The strongest reflections of the powder X-ray diffraction pattern [d,Aa(I)(hkl)] are: 5.902(24)(202), 5.025(24)(020), 3.208(47)(206,132), 3.048(100)(514, 424), 2.758(24)(602) and 2.704(70)(226). The crystal structure, refined from single-crystal X-ray diffraction data (R (sub 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.
