ALBERT

Description: The mineral name "maufite" was proposed in 1930 to describe a "bright emerald green" nickeliferous vein material occurring within a serpentinite of the Great Dyke in the Umvukwe Range of Zimbabwe, then Southern Rhodesia. Study of this material shows that it is not a distinct species but rather an interstratified nickel-bearing lizardite-clinochlore, with lizardite dominant over clinochlore. The name "maufite" is discredited. The lizardite is a Group-A polytype, and the clinochlore is a Ia polytype in the nomenclature developed by S.W. Bailey. The formula calculated on the basis of 14 negative charges is (Mg 1.74 Al 0.88 Ni 0.13 0.25 ) 3.00 (Si 1.60 Al 0.40 ) 2.00 O 5 (OH) 4 ; on the basis of nine oxygen atoms including 14.6 wt.% H 2 O determined thermogravimetrically, the formula is (Mg 1.68 Al 0.78 Ni 0.13 0.41 ) 3.00 (Si 1.55 Al 0.45 ) 2.00 O 4.51 (OH) 4.49 . Analytical electron microscopy shows that the composition is variable on a fine scale. The randomly interstratified lizardite-clinochlore occurs as a pseudomorph after amphibole and plagioclase and is a product of serpentinization. The material is poorly crystalline and very fine grained, producing broad reflections on powder diffraction and microbeam X-ray diffraction patterns. Unlike most of the interstratified serpentine-chlorite described in the literature, lizardite is here dominant over clinochlore.

Description: Peatite-(Y), Li 4 Na1 2 (Y,Na,Ca, HREE ) 12 (PO 4 ) 12 (CO 3 ) 4 (F,OH) 8 , and ramikite-(Y), Li 4 Na 12 (Y,Ca, HREE ) 6 Zr 6 (PO 4 ) 12 (CO 3 ) 4 O 4 (OH,F) 4 , are two new minerals discovered in the core of the Poudrette pegmatite at Mont Saint-Hilaire, Quebec. Epitactic-like, euhedral crystals (pseudocubes) of both minerals range from 0.1 to 1 mm in size (average: 0.2 mm), with ramikite-(Y) forming yellowish-white cores (dominant) and peatite-(Y) occurring as thin (〈 50 um) pale pink rims. Crystals of peatite-(Y) exhibit the dominant forms pinacoid {100}, {010}, and {001} and the m i nor forms rhombic prism {110}, {101}, and {011}, with crystals of ramikite-(Y) showing the possible forms pedion {100}, $$\left\{00\overline{1}\right\}$$ , {010}, $$\left\{0\overline{1}0\right\}$$ , {001}, and $$\left\{00\overline{1}\right\}$$ . The most common associated minerals include albite, rhodochrosite, siderite, chabazite-Na, synchysite-(Ce), and sabinaite. Peatite-(Y) displays a brittle fracture with very good {100}, {010}, and {001} cleavages; ramikite-(Y) has a splintery fracture with possible weak to poor {100}, {010}, and {001} cleavages. Peatite-(Y) has a vitreous luster and ramikite-(Y) has a vitreous to dull luster. Both minerals have a white streak and neither shows any discernible fluorescence under long-, medium-, or short-wave ultraviolet radiation. Both minerals have an approximate Mohs hardness of 3. Peatite-(Y) has a calculated density of 3.62(1) g/cm 3 and ramikite-(Y) of 3.60(1) g/cm 3 . Both minerals have a very low birefringence (~100), exhibit parallel extinction, and give poor interference figures; the optic sign and measured 2 V of both are unknown. Only one refractive index for each could be measured: peatite-(Y), β = 1.601(1) and for ramikite-(Y), β = 1.636 (1). Four analyses of peatite-(Y) gave an average (range) of (wt. %): Li 2 O 1.96 (calc.), Na 2 O 12.95 (12.50–13.30), CaO 1.15 (0.98–1.51), Y 2 O 3 37.32 (37.01–37.52), Gd 2 O 3 0.61 (0.54–0.74), Dy 2 O 3 3.08 (2.91–3.44), Ho 2 O 3 0.67 ( b.d .–1.02), Er 2 O 3 2.88 (2.59–3.15), Tm 2 O 3 0.28 ( b.d .–0.40), Yb 2 O 3 1.78 (1.67–1.92), ZrO 2 0.67 (0.63–0.70), ThO 2 0.37 ( b.d .–0.56), P 2 O 5 27.29 (27.09–27.64), F 4.35 (4.03–4.62), CO 2 5.79 (calc.), H 2 O 0.31 (calc.), O = F –1.83, total 99.75, corresponding to Li 4 Na 12 (Y 10.06 Na 0.72 Ca 0.62 Dy 0.50 Er 0.46 Yb 0.28 Zr 0.17 Ho 0.11 Gd 0.10 Tm 0.04 Th 0.04 Tb 0.02 ) 13.12 (PO 4 ) 11.70 (CO 3 ) 4 [F 6.97 (OH) 1.03 ] 8 and the simplified formula, Li 4 Na 12 (Y,Na,Ca, HREE ) 12 (PO 4 ) 12 (CO 3 ) 4 (F,OH) 8 . For ramikite-(Y), 22 analyses gave an average (range) of (wt. %): Li 2 O 2.01 (calc.), Na 2 O 11.25 (10.32–13.34), CaO 4.15 (4.01–4.27), Y 2 O 3 16.48 (14.88–18.25), La 2 O 3 0.11 ( b.d .–0.48), Ce 2 O 3 0.10 ( b.d .–0.40), Nd 2 O 3 0.08 ( b.d .–031), Dy 2 O 3 1.11 (0.96–1.23), Er 2 O 3 1.18 (1.01–1.36), Yb 2 O 3 0.57 (0.46–0.68), ZrO 2 23.40 (22.66–24.70), ThO 2 0.49 ( b.d .–0.70), HfO 2 0.69 (0.48–0.92), Al 2 O 3 0.14 (0.09–0.22), P 2 O 5 28.10 (27.47–28.58), F 0.62 (0.24–0.90), CO 2 5.92 (calc.), H 2 O 0.92 (calc.), O = F –0.26, total 97.06, corresponding to Li 4 (Na 10.79 Ca 1.21 ) 12 (Y 4.34 Ca 0.99 Dy 0.18 Er 0.18 Yb 0.09 La 0.02 Ce 0.02 Nd 0.01 ) 5.83 (Zr 5.65 Hf 0.10 Th 0.06 ) 5.81 [(P 0.98 Al 0.01 ) 0.99 O 4 ] 12 (CO 3 ) 4 O 4 [(OH) 3.03 F 0.97 ] 4.00 and the simplified formula, Li 4 (Na,Ca) 12 (Y,Ca, HREE ) 6 Zr 6 (PO 4 ) 12 (CO 3 ) 4 O 4 (OH,F) 4 . In both peatite-(Y) and ramikite-(Y), the presence of Li 2 O was confirmed via crystal-structure and LAM-ICP-MS analyses and both H 2 O and CO 2 via results of crystal-structure, infrared, and Raman analyses. Peatite-(Y) crystallizes in space group P 222 with a 11.167(2), b 11.164(2), c 11.162(2) Å, V 1391.7(1) Å 3 , and Z = 1, and ramikite-(Y) in space group P 1 with a 10.9977(6), b 10.9985(6), c 10.9966(6) Å, α 90.075(4), β 89.984(4), 89.969(4)°, V 1330.1(1) Å 3 , and Z = 1. The strongest six lines on the X-ray powder-diffraction pattern [ d in Å ( I ) ( hkl )] for peatite-(Y) are: 4.56(57)(211,121,112), 3.95(57)(220,202,022), 3.54(46) (310,301,130), 2.99(83)(321,312,231), 2.63(100)(330,303,033), 2.149(42)(333) and for ramikite-(Y): 11.04(76)( $$0\overline{1}0$$ ,100, $$00\overline{1}$$ ), 7.80(79)( $$0\overline{1}1$$ ,110,101), 6.36(75) $$(11\overline{1},1\overline{1}1,111,1\overline{11})$$ , 3.89(100)( $$0\overline{2}2$$ ,220,202), 2.94(98) $$(13\overline{2},12\overline{3},23\overline{1})$$ , 2.59(98)( $$0\overline{3}3$$ ,330,303). The crystal structure of peatite-(Y) was refined to R = 3.37% and wR 2 = 9.36% for 3816 reflections and that of ramikite-(Y) to R = 5.13% and wR 2 = 13.06% for 8272 reflections. While not strictly isostructural, both minerals have similar crystal structures dominated by M 8 polyhedra ( M = Y,Zr; = unspecified ligand). These are linked into six-membered, edge- or corner-sharing clusters, which in turn are joined together by PO 4 tetrahedra. Both LiO 6 octahedra and CO 3 groups are positioned within the corner-sharing clusters. Linkages among all these polyhedra produce an open, equidimensional framework structure, with Na occupying the resulting cavities. Although possessing complex crystal structures, both minerals may be considered more simply as homeotypes of body-centered cubic Fe (or CsCl) or, alternatively, as complex derivatives of cation-deficient perovskite-related structures. Both minerals are late-stage products, possibly related to the in situ alteration of the pre-existing mineral assemblage (dawsonite, burbankite-group minerals, sabinaite, muscovite-polylithionite, etc .) present in the core of the Poudrette pegmatite.

Description: Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 µm in size. The crystals occur as aggregates (up to 500 µm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3–4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm -3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are a = 1.671, ß = 1.687, ? = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r 〈 v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1I, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, a = 84.2892(9), ß = 90.4920(9), ? = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1I10); 7.526, 71, (010); 2.974, 49, (200, 022I); 3.253, 40, (021, 120); 2.701, 39, (2I10, 002, 1I2I1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)S2.92As2.03O8(H2O)4.The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKa radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

Description: Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 µm in size. The crystals occur as aggregates (up to 500 µm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3–4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm -3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are a = 1.671, ß = 1.687, ? = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r 〈 v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1I, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, a = 84.2892(9), ß = 90.4920(9), ? = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1I10); 7.526, 71, (010); 2.974, 49, (200, 022I); 3.253, 40, (021, 120); 2.701, 39, (2I10, 002, 1I2I1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)S2.92As2.03O8(H2O)4.The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKa radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

Description: Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as thin platy crystals up to 80 μm long and a few μm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across. It is associated with coarse white leiteite, dark blue köttigite, minor legrandite and adamite. Ianbruceite is sky blue to very pale blue with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. It has perfect cleavage parallel to (100), is flexible, and deforms plastically. The Mohs hardness is 1 and the calculated density is 3.197 g cm−3. The refractive indices are α = 1.601, β = 1.660, γ = 1.662, all ±0.002; 2Vobs = 18(2)°, 2Vcalc = 20°, and the dispersion is r 〈 v, weak. Ianbruceite is monoclinic, space group P21/c, a = 11.793(2), b = 9.1138(14), c = 6.8265(10) Å, β = 103.859(9)°, V = 712.3(3) Å3, Z = 4, a:b:c = 1.2940:1:0.7490. The seven strongest lines in the X-ray powder diffraction pattern [d (Å), I, (hkl)] are as follows: 11.29, 100, (100); 2.922, 17, (130); 3.143, 15, (2İ02); 3.744, 11, (300); 2.655, 9, (230); 1.598, 8, (1İ52); 2.252, 7, (222). Chemical analysis by electron microprobe gave As2O5 36.27, As2O3 1.26, Al2O3 0.37, ZnO 49.72, MnO 0.32, FeO 0.71, K2O 0.25, H2Ocalc 19.89, sum 108.79 wt.%; the very high oxide sum is due to the fact that the calculated H2O content is determined from crystal-structure analysis, but H2O is lost under vacuum in the electron microprobe.The crystal structure of ianbruceite was solved by direct methods and refined to an R1 index of 8.6%. The As is tetrahedrally coordinated by four O anions with a mean As–O distance of 1.687 Å. Zigzag [[5]Zn[6]Znφ7] chains extend in the c direction and are linked in the b direction by sharing corners with (AsO4) tetrahedra to form slabs with a composition [Zn2(OH)(H2O)(AsO4)]. The space between these slabs is filled with disordered (H2O) groups and minor lone-pair stereoactive As3+. The ideal formula derived from chemical analysis and crystal-structure solution and refinement is [Zn2(OH)(H2O)(AsO4)](H2O)2.

Description: Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 µm in size. The crystals occur as aggregates (up to 500 µm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3–4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm -3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are a = 1.671, ß = 1.687, ? = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r 〈 v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1I, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, a = 84.2892(9), ß = 90.4920(9), ? = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1I10); 7.526, 71, (010); 2.974, 49, (200, 022I); 3.253, 40, (021, 120); 2.701, 39, (2I10, 002, 1I2I1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)S2.92As2.03O8(H2O)4.The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKa radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

Description: The crystal structure of yofortierite, (Mn 2+ ,Mg,Fe 3+ ,) 5 Si 8 O 20 (OH,H 2 O) 2 (H 2 O) 7 , monoclinic, C 2/ m , Z = 4, a 14.1686(12), b 17.8583(16), c 5.2919(5) Å, β 105.878(1)°, V 1287.9(3) Å 3 , has been refined to R 1 = 4.9 % for 1795 unique ( F o 〉 4 F ) reflections collected on a Bruker D8 three-circle diffractometer equipped with a rotating-anode generator (Mo K α X-radiation), a multi-layer optics incident-beam path, and an APEX-II CCD detector. Chemical analysis by electron microprobe plus Fe 3+ determination by Mössbauer spectroscopy gave SiO 2 51.78, Al 2 O 3 0.05, TiO 2 0.15, Fe 2 O 3 1.84, MnO 22.97, ZnO 0.99, MgO 4.32, CaO 1.10, H 2 O calc 16.69, sum 99.89 wt.%. The resulting empirical formula is (Mn 3.01 Mg 1.00 Zn 0.11 Ca 0.18 Fe 3+ 0.21 Ti 0.02 Al 0.01 0.46 ) =5 Si 8.00 O 20 [(OH) 1.34 (H 2 O) 0.66 ] =2 (H 2 O) 7 . Yofortierite is a palygorskyite-group mineral. There are two tetrahedrally coordinated T sites occupied by Si with 〈Si–O〉 distances of 1.621 and 1.617 Å, and three octahedrally coordinated M sites, occupied primarily by Mn 2+ and Mg with minor Fe 3+ and , with 〈 M –O〉 distances of 2.147, 2.079, and 2.183 Å. The 〈 M –O〉 distances indicate strong order of M cations over the three M sites, with the smaller cations and vacancies ordered at the M (2) site and Ca ordered at the M (3) site. The presence of vacancies at the M (2) site locally couple with the replacement of (OH) – at the O(4) site by (H 2 O) o , giving rise to strong short-range order, and H 2 O is incorporated into the framework part of the structure by the substitution Mn 2+ + (OH) – = + (H 2 O) o which is coupled to the substitution Mn 2+ = Fe 3+ by the requirement of electroneutrality.

Description: The chemical composition and chemical formula for ferro-ferri-nybøite given by Lussier et al . (2014) are wrong due to incorporation of errors during preparation of the paper. The data given in the original IMA submission are correct and are given here: SiO 2 47.06, TiO 2 0.50, Al 2 O 3 3.16, Fe 2 O 3 12.43, FeO 22.37, (Fe tot = 33.56), MnO 2.18, ZnO 0.06, MgO 0.23, CaO 1.03, Na 2 O 8.15, K 2 O 1.72, F 0.84, H 2 O calc 1.50, O F –0.35 sum 100.88 wt.%. The formula unit, calculated on the basis of 24 (O + OH + F) with (OH + F) = 2 apfu , is (Na 0.67 K 0.35 )(Na 1.83 Ca 0.17 )(Mg 0.05 Fe 2+ 2.96 Mn 0.29 Zn 0.01 Al 0.03 Fe 3+ 1.48 Ti 0.06 )(Si 7.44 Al 0.56 )O 22 (OH 1.58 F 0.42 ).

Description: Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as thin platy crystals up to 80 μm long and a few μm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across. It is associated with coarse white leiteite, dark blue köttigite, minor legrandite and adamite. Ianbruceite is sky blue to very pale blue with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. It has perfect cleavage parallel to (100), is flexible, and deforms plastically. The Mohs hardness is 1 and the calculated density is 3.197 g cm−3. The refractive indices are α = 1.601, β = 1.660, γ = 1.662, all ±0.002; 2Vobs = 18(2)°, 2Vcalc = 20°, and the dispersion is r 〈 v, weak. Ianbruceite is monoclinic, space group P21/c, a = 11.793(2), b = 9.1138(14), c = 6.8265(10) Å, β = 103.859(9)°, V = 712.3(3) Å3, Z = 4, a:b:c = 1.2940:1:0.7490. The seven strongest lines in the X-ray powder diffraction pattern [d (Å), I, (hkl)] are as follows: 11.29, 100, (100); 2.922, 17, (130); 3.143, 15, (2İ02); 3.744, 11, (300); 2.655, 9, (230); 1.598, 8, (1İ52); 2.252, 7, (222). Chemical analysis by electron microprobe gave As2O5 36.27, As2O3 1.26, Al2O3 0.37, ZnO 49.72, MnO 0.32, FeO 0.71, K2O 0.25, H2Ocalc 19.89, sum 108.79 wt.%; the very high oxide sum is due to the fact that the calculated H2O content is determined from crystal-structure analysis, but H2O is lost under vacuum in the electron microprobe.The crystal structure of ianbruceite was solved by direct methods and refined to an R1 index of 8.6%. The As is tetrahedrally coordinated by four O anions with a mean As–O distance of 1.687 Å. Zigzag [[5]Zn[6]Znφ7] chains extend in the c direction and are linked in the b direction by sharing corners with (AsO4) tetrahedra to form slabs with a composition [Zn2(OH)(H2O)(AsO4)]. The space between these slabs is filled with disordered (H2O) groups and minor lone-pair stereoactive As3+. The ideal formula derived from chemical analysis and crystal-structure solution and refinement is [Zn2(OH)(H2O)(AsO4)](H2O)2.

Description: A bstract Ferro-ferri-nybøite, NaNa 2 (Fe 2+ 3 Fe 3+ 2 )Si 8 O 22 (OH) 2 , is a new mineral of the amphibole group from Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie (formerly Rouville County), Québec, 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 greyish-green to black streak. Ferro-ferri-nybøite 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/cm 3 . Crystals show extreme optical absorption due to intervalence charge transfer, which inhibited measurement of optical properties. Ferro-ferri-nybøite is monoclinic, space group C 2/ m , a 9.9190(5), b 18.0885(8), c 5.3440(3) Å, β 103.813(1)°, V 931.09(13) Å 3 , Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [ d in Å( 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)( 2{macron} 02), 2.344(9)( 3{macron} 51), 3.298(7)(240), 2.606(6)(061), 1.446(6)( 6{macron} 61,4.10.0). Analysis by a combination of electron microprobe and Mössbauer spectroscopy gives SiO 2 45.80, Al 2 O 3 3.11, TiO 2 0.50, Fe 2 O 3 11.18, FeO 23.45, MnO 2.28, ZnO 0.12, MgO 0.23, CaO 0.99, Na 2 O 8.01, K 2 O 1.30, F 0.81, H 2 O calc 1.47, 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 (Na 0.68 K 0.27 ) 0.95 (Na 1.83 Ca 0.17 ) 2.00 (Mg 0.06 Fe 2+ 3.17 Mn 0.31 Zn 0.01 Fe 3+ 1.36 Ti 0.06 ) 4.97 (Si 7.41 Al 0.59 ) 8.00 O 22 (OH 1.58 F 0.42 ) 2.00 . Ferro-ferri-nybøite, ideally NaNa 2 (Fe 2+ 3 Fe 3+ 2 )Si 8 O 22 (OH) 2 , is related to endmember nybøite, NaNa 2 (Mg 3 Al 2 )Si 8 O 22 (OH) 2 by the substitutions Fe 2+ -〉 Mg and Fe 3+ -〉 Al.