Publication Type:

Journal Article


Canadian Mineralogist, Mineralogical Association of Canada, Volume 52, Number 6, p.1019-1026 (2014)




Alumina, Aluminum oxide, Brittle fracture, Charge transfer, crystal structure, Electron probe microanalysis, Feldspar, Hematite, II-VI semiconductors, Light absorption, Magnesia, Manganese oxide, optical properties, silica, Sodium compounds, Titanium dioxide, X ray diffraction, Zinc oxide


Ferro-ferri-nyboite, NaNa2(Fe32+Fe23+)Si8O22(OH)2, is a new mineral of the amphibole group from Poudrette quarry, Mont Saint-Hilaire, La Vallee-du-Richelieu RCM, Monteregie (formerly Rouville County), Quebec, Canada. It occurs in an igneous microbreccia associated with a eudialyte-group mineral, an astrophyllite-group mineral, albite, and nepheline. Crystals are prismatic parallel to [001] with {100} and {110} forms and cleavage surfaces, and the prism direction is terminated by irregular fractures. Grains are up to 3 cm long, and occur as blocky aggregates. Crystals are black with a greyishgreen to black streak. Ferro-ferri-nyboite is brittle, has a Mohs hardness of 6 and a splintery fracture; it is non-fluorescent with perfect {110} cleavage, no observable parting, and has a calculated density of 3.424 g/cm3. Crystals show extreme optical absorption due to intervalence charge transfer, which inhibited measurement of optical properties. Ferro-ferri-nyboite is monoclinic, space group C2/m, a 9.9190(5), b 18.0885(8), c 5.3440(3) A, 103.813(1), V 931.09 (13) A3, Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d in A(I)(hkl)]: 8.520(100)(110), 3.162 (55)(310), 2.834(24)(330), 1.671(19)(461), 2.732(10)(151), 2.552(10)(202), 2.344(9)(351), 3.298(7)(240), 2.606(6)(061), 1.446(6)(661,4.10.0). Analysis by a combination of electron microprobe and Mossbauer spectroscopy gives SiO245.80, Al2O33.11, TiO20.50, Fe2O311.18, FeO 23.45, MnO 2.28, ZnO 0.12, MgO 0.23, CaO 0.99, Na2O 8.01, K2O 1.30, F 0.81, H2Ocalc1.47, O F-0.34 sum 98.91 wt.%. The formula unit, calculated on the basis of 24 (O + OH + F) with (OH + F) = 2 apfu is (Na0.68K0.27)0.95(Na1.83Ca0.17)2.00(Mg0.06Fe32+.17Mn0.31Zn0.01Fe1.363+Ti0.06)4.97(Si7.41Al0.59)8.00O22(OH1.58F0.42)2.00. Ferroferri-nyboite, ideally NaNa2(Fe32+Fe23+)Si8O22(OH)2, is related to endmember nyboite, NaNa2(Mg3Al2)Si8O22(OH)2by the substitutions Fe2+ Mg and Fe3+ Al.


Compilation and indexing terms, Copyright 2018 Elsevier Inc.<br/>20153101104573<br/>Canada<br/>Crystal structure refinement<br/>Mont Saint-Hilaire<br/>New amphiboles<br/>Ssbauer spectroscopies