Fluorarrojadite-(BaNa), BaNa4CaFe13Al(PO4)(11)(PO3OH)F-2, a new member of the arrojadite group from Gemerska Poloma, Slovakia

摘要

The new mineral fluorarrojadite-(BaNa), ideally BaNa4CaFe13Al(PO4)(11)(PO3OH)F-2 was found on the dump of Elisabeth adit near Gemerska Poloma, Slovakia. It occurs in hydrothermal quartz veins intersecting highly fractionated, topaz-zinnwaldite S-type leucogranite. Fluorannjadite-(BaNa) is associated with fluorapatite,'fluordickinsonite-(BaNa)', triplite, viitaniemiite and minor amounts of other minerals. It forms fme-grained irregular aggregates up to 4 cm x 2 cm, which consist of individual anhedral grains up to 0.01 mm in size. It has a yellowish-brown to greenish-yellow colour, very pale yellow streak and a vitreous to greasy lustre. Mobs hardness is similar to 41/2 to 5. The fracture is irregular and the tenacity is brittle. The measured density is 3.61(2) g cm (3) and calculated density is 3.650 g cm (3). Fluorarrojadite-(BaNa) is biaxial (+) and nonpleoclunic. The calculated refractive index based on empirical formula is 1.674. The empirical formula (based on 47 O and 3 (OH + F) apfu) is (A1)(Ba0.65K0.35) Sigma 1.00(A2)Na(0.35)(B)(1)(Na0.54Fe0.46)(Sigma 1.00)Na-B2(0).54(Ca)(Ca0.7Sr0.20Pb0.02Ba0.04)(Sigma 1.00)(Na2Na0.46)-Na-Na3 M(Fe7.16Mn5.17Li0.37Mg0.12SC0.08Zn0.06Ga0.02Ti0.02)Sigma(1)(3.00) Al1.02P11O44PO3.46(OH)(0.54)(F1.54OH0.46).Fluorannjadite-(BaNa) is monoclinic, space group Cc, a = 16.563(1) (A)overcircle, b = 10.0476(6) (A)overcircle, c = 24.669(1) (A)overcircle, p= 105.452(4)degrees, V=3957.5(4) (A)overcircle(3) and Z=4. The seven strongest reflections in the powder X-ray diffraction pattern are [d(obs) in (A)overcircle, (I) hkl]: 3.412, (21), 116; 3.224, (37), 206; 3.040, (100), 42 (4) over bar; 2.8499, (22), 33 (3) over bar; 2.7135, (56), 226; 2.5563, (33), 028 and 424; 2.5117, (23), 040. The new mineral is named according to the nomenclature scheme of arrojadite-group minerals, approved by the IMA CNMNC. In fluorarrojadite-(BaNa), Fe2+ is a dominant cation at the M site (so the root-name is arrojadite) and two suffixes are added to the root-name according to the dominant cation of the dominant valence state at the Al (Ba2+) and B1 sites (Na+). A prefix fluor is added to the root-name as F is dominant over (OH) at the W site.