Natropalermoite, Na2SrAl4(PO4)(4)(OH)(4), a new mineral isostructural with palermoite, from the Palermo No. 1 mine, Groton, New Hampshire, USA

Natropalermoite, ideally Na2SrAl4(PO4)(4)(OH)(4), the Na-analogue of palermoite, is a new mineral from the Palermo No. 1 mine, Groton, New Hampshire, USA. Associated minerals are palermoite, eosphorite and quartz. Natropalermoite crystals are prismatic with striations parallel to the direction of elongation (the a axis) up to 200 mu m x 50 mu m x 45 mu m in size. The mineral is colourless, transparent with a white streak and vitreous lustre and is visually indistinguishable from palermoite. It is brittle with subconchoidal fracture and has a Mohs hardness of 5.5. Cleavage is perfect on {001}, fair on {100} and no parting was observed. The calculated density is 3.502 g cm(-3). Natropalermoite is biaxial (-), alpha = 1.624(1), ss = 1.641(1), gamma = 1.643(1) (589 nm), 2V(meas) = 43(4)degrees, 2V(calc) = 38 degrees. An electronmicroprobe analysis yielded an empirical formula (based on 20 O apfu) of (Na1.69Li0.31)(Sigma 2.00) (Sr0.95Mg0.04C a(0.02)Ba(0.01))(Sigma 1.02) (Al3.82Mn0.03Fe0.03)(Sigma 3.88) (P1.01O4)(4)(OH)(4). Natropalermoite is orthorhombic, space group Imcb, a = 11.4849(6), b = 16.2490(7), c = 7.2927(4) angstrom, V = 1360.95(17) A(3), Z = 4. Natropalermoite is isotypic with palermoite, but substitution of the larger Na for Li results in substantial increase of the b cell parameter. Four of the seven Na-O distances are longer than their equivalents in palermoite, resulting in a more regular 7-fold coordination polyhedron about Na. The eight strongest peaks in the calculated X-ray powder diffraction are [d(calc) (angstrom), I-rel%, (hkl)]: [3.128, 100, (321)], [4.907, 68, (121)], [3.327, 48, (022)], [4.689, 45, (220)], [3.078, 45, (202)], [2.453, 38, (242)], [2.636, 35, (411)], [2.174, 35, (422)].12 month embargo; published online: 01 August 2018.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A new formula and crystal structure for nickelskutterudite, (Ni,Co,Fe)As-3, and occupancy of the icosahedral cation site in the skutterudite group

We propose a new formula for the mineral nickelskutterudite, based on our observation that either (or both) Co or Fe3+ are essential structure constituents. The crystal structure of nickelskutterudite, (Ni,Co,Fe) As-3, cubic, Im (3) over bar, Z = 8: a = 8.2653(6) angstrom, V = 564.65(7) angstrom, has been refined to R-1 = 1.4% for 225 unique reflections I > 2 sigma(1) collected on a Bruker X8 four-circle diffractometer equipped with fine-focus, sealed tube MoKa radiation and an APEX-II CCD detector. This is the first report of the crystal structure of nickelskutterudite. Nickelskutterudite, a member of the skutterudite group of isostructural minerals, adopts a distorted perovskite structure with notably tilted octahedra and an unoccupied to partially occupied icosahedral metal site. In the structure of nickelskutterudite, there is one metal (B) site occupied by Ni, Co, or Fe in octahedral coordination with six As atoms. Procrystal electron density analysis shows each As anion is bonded to two cations and two As anions, resulting in a four-membered ring of bonded As with edges 2.547 and 2.475 angstrom. The extreme tilting of BAs6 octahedra is likely a consequence of the As-As bonding. The nickelskutterudite structure differs from the ideal perovskite structure (A(4)B(4)X(12)) in that As4 anion rings occupy three of the four icosahedral cages centered on the A sites. There are reported synthetic phases isomorphous with skutterudite with the other A site completely occupied by a cation (AB(4)X(12)). Electron microprobe analyses of nickelskutterudite gave an empirical chemical formula of (Ni0.62Co0.28Fe0.12)(Sigma 1.02)(AS(2.95)S(0.05))(Sigma 3.00) normalized to three anions. Pure NiAs3 nickelskutterudite, natural or synthesized, has not been reported. In nature, nickelskutterudite is always observed with significant Co and Fe, reportedly because all non-bonded valence electrons must be spin-paired. This suggests that nickelskutterudite must contain Co3+ and Fe2+, consistent with previous models since Ni4+ cannot spin-pair its seven non-bonded electrons, Co3+ and Fe2+, which can spin-pair all non-bonded electrons, are required to stabilize the structure. No anion deficiencies were found in the course of this study so, including the structurally necessary Co and Fe, the chemical formula of nickelskutterudite (currently given as NiAs3-x, by the IMA) should be considered (Ni,Co,Fe)As-3.Freeport McMoRan; Mineralogical Society of America Krauss Crystallographic Research Grant; Brazilian government [FAPESP 2013/03487-8]12 month embargo; First Published on January 03, 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Fluorlamprophyllite, Na-3(SrNa)Ti-3(Si2O7)(2)O2F2, a new mineral from Pocos de Caldas alkaline massif, Morro do Serrote, Minas Gerais, Brazil

A new mineral species, fluorlamprophyllite (IMA2013-102), ideally Na3(SrNa)Ti-3(Si2O7)(2)O2F2, has been found in the Pocos de Caldas alkaline massif, Morro do Serrote, Minas Gerais, Brazil. Alternatively, the idealized chemical formula could be written as (SrNa)[(Na3Ti)F-2][Ti-2(Si2O7)(2)O-2], setting the large interlayer cations before the cations of the layer. Fluorlamprophyllite is the F-analogue of lamprophyllite. It is associated with aegirine, analcime, natrolite, nepheline and microcline. Fluorlamprophyllite crystals are brownish-orange and bladed. The mineral is transparent with a pale yellow streak and an adamantine lustre. It is brittle and has a Mohs hardness of similar to 3; cleavage is perfect on {100} and no parting was observed. The calculated density is 3.484 g/cm(3). Optically, fluorlamprophyllite is biaxial (+), with alpha= 1.735(7), beta = 1.749(7) and gamma = 1.775(9) and 2V(meas) = 72(3)degrees. An electron microprobe analysis produced an average composition (wt.%) (9 points) of Na2O 10.63(30), K2O 0.47(3), SiO2 30.51(13), SrO 18.30(24), MgO 0.81(17), Al2O3 0.23(2), CaO 1.11(7), MnO 5.03(38), TiO2 27.41(87), Fe2O3 2.45(37), F 2.86(23), plus H2O 1.00 (added to bring the total close to 100%), O = F 1.20, with the total = 98.61%. The elements Nb and Ba were sought, but contents were below microprobe detection limits. The resultant chemical formula was calculated on the basis of 18 (O + F) atoms per formula unit. The addition of 1.00 wt.% H2O brought [F+(OH)] = 2 pfu, yielding (Na2.63Sr1.35Mn0.54Ca0.15Mg0.15K0.08)(Sigma 4.90)(Ti2.63Fe0.24Al0.04)(Sigma 2.91)Si3.89O16[F-1.15(OH)(0.85)](Sigma 2.00). The mineral is monoclinic, with space group C2/m and unit-cell parameters a - 19.255(2), b - 7.0715(7), c - 5.3807(6) A, beta = 96.794(2)degrees and V = 727.5(1) A(3). The structure is a layered silicate inasmuch as the O atoms are arranged in well-defined, though not necessarily close-packed layers.Science Foundation Arizona; CNPQ; Sao Paulo Research Foundation [2013/03487-8]12 month embargo; published online: 28 February 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Scapula fractures: interobserver reliability of classification and treatment

OBJECTIVES:There is substantial variation in the classification and the management of scapula fractures. The first purpose of this study was to analyze the interobserver reliability of the OTA/AO and the New International Classification of scapula fractures. The second purpose was to assess the proportion of agreement among orthopaedic surgeons on operative or nonoperative treatment. DESIGN:: Web-based reliability study SETTING:: Independent orthopaedic surgeons from several countries were invited to classify scapular fractures in an online survey. PARTICIPANTS:One-hundred and three orthopaedic surgeons evaluated 35 movies of 3DCT-reconstruction of selected scapular fractures, representing a full spectrum of fracture patterns. MAIN OUTCOME MEASUREMENTS:Fleiss' kappa (κ) was used to assess the reliability of agreement between the surgeons. RESULTS:: The overall agreement on the OTA/AO Classification was moderate for the types (A, B, and C, κ = 0.54) with a 71% proportion of rater agreement (PA) as well as for the nine groups (A1 to C3, κ = 0.47) with a 57% PA. For the New International Classification, the agreement about the intra-articular extension of the fracture (Fossa (F), κ = 0.79) was substantial, the agreement about a fractured body (Body (B), κ = 0.57) or process was moderate (Process (P), κ = 0.53), however PAs were more than 81%. The agreement on the treatment recommendation was moderate (κ = 0.57) with a 73% PA. CONCLUSIONS:The New International Classification was more reliable. Body and process fractures generated more disagreement than intra-articular fractures and need further clear definitions