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Vera Rubin ridge (VRR) is an erosion‐resistant feature on the northwestern slope of Mount Sharp in Gale crater, Mars, and orbital visible/short‐wave infrared measurements indicate it contains red‐colored hematite. The Mars Science Laboratory Curiosity rover performed an extensive campaign on VRR to study its mineralogy, geochemistry, and sedimentology to determine the depositional and diagenetic history of the ridge and constrain the processes by which the hematite could have formed. X‐ray diffraction (XRD) data from the CheMin instrument of four samples drilled on and below VRR demonstrate differences in iron, phyllosilicate, and sulfate mineralogy and hematite grain size. Hematite is common across the ridge, and its detection in a gray‐colored outcrop suggested localized regions with coarse‐grained hematite, which commonly forms from warm fluids. Broad XRD peaks for hematite in one sample below VRR and the abundance of FeO_T in the amorphous component suggest the presence of nano‐crystalline hematite and amorphous Fe oxides/oxyhydroxides. Well‐crystalline akaganeite and jarosite are present in two samples drilled from VRR, indicating at least limited alteration by acid‐saline fluids. Collapsed nontronite is present below VRR, but samples from VRR contain phyllosilicate with d(001) = 9.6 A, possibly from ferripyrophyllite or an acid‐altered smectite. The most likely cementing agents creating the ridge are hematite and opaline silica. We hypothesize late diagenesis can explain much of the mineralogical variation on the ridge, where multiple fluid episodes with variable pH, salinity, and temperature altered the rocks, causing the precipitation and crystallization of phases that are not otherwise in equilibrium.

International audience; The Mars Science Laboratory Curiosity rover arrived at Mars in August 2012 with a primary goal of characterizing the habitability of ancient and modern environments. Curiosity was sent to Gale crater to study a sequence of ∼3.5 Ga old sedimentary rocks that, based on orbital visible and near- to short-wave infrared reflectance spectra, contain secondary minerals that suggest deposition and/or alteration in liquid water. The sedimentary sequence in the lower slopes of Mount Sharp in Gale crater preserves a dramatic shift on early Mars from a relatively warm and wet climate to a cold and dry climate, based on a transition from smectite-bearing strata to sulfate-bearing strata. The rover is equipped with instruments to examine the sedimentology and identify compositional changes in the stratigraphy. The Chemistry and Mineralogy (CheMin) instrument is one of two internal laboratories on Curiosity and includes a transmission X-ray diffractometer (XRD) and X-ray fluorescence (XRF) spectrometer. CheMin measures loose sediment samples scooped from the surface and drilled rock powders, and the XRD provides quantitative mineralogy to a detection limit of ∼1 wt.% for crystalline phases. Curiosity has traversed >20 km since landing and has primarily been exploring an ancient lake environment fed by streams and groundwater. Of the 19 drilled rock samples analyzed by CheMin as of sol 2300 (January 2019), 15 are from fluvio-lacustrine deposits that comprise the Bradbury and Murray formations. Most of these samples were drilled from units that did not have a clear mineralogical signature from orbit. Results from CheMin demonstrate an astounding diversity in the mineralogy of these rocks that signifies geochemical variations in source rocks, transportation mechanisms, and depositional and diagenetic fluids. Most detrital igneous minerals are basaltic, but the discovery in a few samples of abundant silicate minerals that usually crystallize from evolved magmas on Earth remains enigmatic. Trioctahedral smectite and magnetite at the base of the section may have formed from low-salinity pore waters with a circumneutral pH in lake sediments. A transition to dioctahedral smectite, hematite, and Ca-sulfate going up section suggests a change to more saline and oxidative aqueous conditions in the lake waters themselves and/or in diagenetic fluids. Perhaps one of the biggest mysteries revealed by CheMin is the high abundance of X-ray amorphous materials (15–73 wt.%) in all samples drilled or scooped to date. CheMin has analyzed three modern eolian sands, which have helped constrain sediment transport and mineral segregation across the active Bagnold Dune Field. Ancient eolian sandstones drilled from the Stimson formation differ from modern eolian sands in that they contain abundant magnetite but no olivine, suggesting that diagenetic processes led to the alteration of olivine to release Fe(II) and precipitate magnetite. Fracture-associated halos in the Stimson and the Murray formations are evidence for complex aqueous processes long after the streams and lakes vanished from Gale crater. The sedimentology and composition of the rocks analyzed by Curiosity demonstrate that habitable environments persisted intermittently on the surface or in the subsurface of Gale crater for perhaps more than a billion years.

This is a comprehensive compilation of refractive indices of 1933 minerals and 1019 synthetic compounds including exact chemical compositions and references taken from 30 compilations and many mineral and synthetic oxide descriptions. It represents a subset of about 4000 entries used by Shannon and Fischer (2016) to determine the polarizabilities of 270 cations and anions after removing 425 minerals and compounds containing the lone-pair ions (Tl + , Sn 2+ , Pb 2+ , As 3+ , Sb 3+ , Bi 3+ , S 4+ , Se 4+ , Te 4+ , Cl 5+ , Br 5+ , I 5+ ) and uranyl ions, U 6+ . The table lists the empirical composition of the mineral or synthetic compound, the ideal composition of the mineral, the mineral name or synthetic compound, the Dana classes and subclasses extended to include beryllates, aluminates, gallates, germanates, niobates, tantalates, molybdates, tungstates, etc., descriptive notes, e.g., structure polytypes and other information that helps define a particular mineral sample, and the locality of a mineral when known. Finally, we list n x , n y , n z , n Dobs > (all determined at 589.3 nm), n Dcalc >, deviation of observed and calculated mean refractive indices, molar volume V m , corresponding to the volume of one formula unit, anion molar volume V an , calculated from V m divided by the number of anions (O 2− , F − , Cl − , OH − ) and H 2 O in the formula unit, the total polarizability AE >, and finally the reference to the refractive indices for all 2946 entries. The total polarizability of a mineral, AE >, is a useful property that reflects its composition, crystal structure, and chemistry and was calculated using the Anderson-Eggleton relationship α AE = ( n D 2 - 1 ) V m 4 π + ( 4 π 3 - c ) ( n D 2 - 1 ) where c = 2.26 is the electron overlap factor. The empirical polarizabilities and therefore, the combination of refractive indices, compositions, and molar volumes of the minerals and synthetic oxides in the table were verified by a comparison of observed and calculated total polarizabilities, AE > derived from individual polarizabilities of cations and anions. The deviation between observed and calculated refractive indices is

Hemihedrite from the Florence Lead-Silver mine in Pinal County, Arizona, USA was first described and assigned the ideal chemical formula Pb10Zn(CrO4)6(SiO4)2F2, based upon a variety of chemical and crystal-structure analyses. The primary methods used to determine the fluorine content for hemihedrite were colorimetry, which resulted in values of F that were too high and inconsistent with the structural data, and infrared (IR) spectroscopic analysis that failed to detect OH or H2O. Our reinvestigation using electron microprobe analysis of the type material, and additional samples from the type locality, the Rat Tail claim, Arizona, and Nevada, reveals the absence of fluorine, while the presence of OH is confirmed by Raman spectroscopy. These findings suggest that the colorimetric determination of fluorine in the original description of hemihedrite probably misidentified F due to the interferences from PO4and SO4, both found in our chemical analyses. As a consequence of these results, the study presented here proposes a redefinition of the chemical composition of hemihedrite to the ideal chemical formula Pb10Zn(CrO4)6(SiO4)2(OH)2. Hemihedrite is isotypic with iranite with substitution of Zn for Cu, and raygrantite with substitution of Cr for S. Structural data from a sample from the Rat Tail claim, Arizona, indicate that hemihedrite is triclinic in space groupP1,a= 9.4891(7),b= 11.4242(8),c= 10.8155(7) Å, α = 120.368(2)°, β = 92.017(3)°, γ = 55.857(2)°,V= 784.88(9) Å3,Z= 1, consistent with previous investigations. The structure was refined from singlecrystal X-ray diffraction data toR1= 0.022 for 5705 unique observed reflections, and the ideal chemical formula Pb10Zn(CrO4)6(SiO4)2(OH)2was assumed during the refinement. Electron microprobe analyses of this sample yielded the empirical chemical formula Pb10.05(Zn0.91Mg0.02)∑ = 0.93(Cr5.98S0.01P0.01)∑ = 6.00Si1.97O34H2.16based on 34 O atoms and six (Cr + S + P) per unit cell.

Gypsum (CaSO4·2H2O) has been identified as a major component of part of Olympia Undae in the northern polar region of Mars, along with the mafic minerals more typical of Martian dune fields. The source and age of the gypsum is disputed, with the proposed explanations having vastly different implications for Mars’ geological history. Furthermore, the transport of low density gypsum grains relative to and concurrently with denser grains has yet to be investigated in an aeolian setting. To address this knowledge gap, we performed a field study at White Sands National Monument (WSNM) in New Mexico, USA. Although gypsum dominates the bulk of the dune field, a dolomite-rich [CaMg(CO3)2] transport pathway along the northern border of WSNM provides a suitable analog site to study the transport of gypsum grains relative to the somewhat harder and denser carbonate grains. We collected samples along the stoss slope of a dune and on two coarse-grained ripples at the upwind margin of the dune field where minerals other than gypsum were most common. For comparison, additional samples were taken along the stoss slope of a dune outside the dolomite transport pathway, in the center of the dune field. Visible and near-infrared (VNIR), X-ray powder diffraction (XRD), and Raman analyses of different sample size fractions reveal that dolomite is only prevalent in grains larger than ∼1 mm. Other minerals, most notably calcite, are also present in smaller quantities among the coarse grains. The abundance of these coarse grains, relative to gypsum grains of the same size, drops off sharply at the upwind margin of the dune field. In contrast, gypsum dominated the finer fraction (

Meierite, ideally Ba44Si66Al30O192Cl25(OH)33, is a new mineral from the Gun claim, just south of the Itsi Range, Yukon, Canada. Meierite occurs as equant grains up to 200 μm across, enclosed within large gillespite crystals. The mineral is transparent, has a vitreous luster, and is non-fluorescent. It has a white streak and Mohs hardness of approximately 5½. It is brittle with no observed cleavage. The calculated density based upon the chemical formula and single-crystal unit-cell dimension is 3.50 g/cm3. The mineral is optically isotropic ( n = 1.598) Electron-microprobe composition (average of 11): SiO2 28.30, P2O5 1.61, Al2O3 11.75, TiO2 0.05, FeO 0.27, CaO 0.21, BaO 47.61, Na2O 0.15, K2O 0.21, Cl 6.64, and a total of 95.29 wt.%. The empirical formula (based on 192 framework O apfu ) and charge balance considerations is: Ba41.1Ca0.5Fe0.5Na0.7K0.6Si62.5Al30.5P3.0O192Cl24.8·33.4(OH). It is possible that additional H2O molecules are located within the cavities in the structure. Meierite is cubic, Im 3¯ m , a 18.5502(4) A, V 6383.3(2) A3, and Z = 1. The 10 most intense lines in the X-ray powder diffraction pattern are [ d obs in A( I )( hkl )]: 4.39(70)(411), 4.16(26)(420), 3.798(25)(422), 3.288(34)(440), 3.189(100)(433), 3.016(72)(611), 2.803(42)(622), 2.629(31)(710), 2.323(46)(800), and 2.287(59)(741). The crystal structure ( R = 4.1% for 1393 F o > 4σ F ) is a three dimensional framework of silicon-, aluminium-, and phosphorous-containing tetrahedra that create an open framework consisting of a large cubo-octahedral cavity connected by channels composed of double eight-membered rings and double six-membered rings. The aluminosilicate framework is isostructural with that observed for silicate framework type ZK-5 (KFI). The mineral is named in honor of Walter M. Meier (1926–2009), a pioneer in zeolite research.

In this study, electrospun polycaprolactone (PCL) fibers are plasma-treated and chemically conjugated with cholesteryl succinyl silane (CSS). In addition to Raman spectroscopy, an immobilization study of DiO as a fluorescent probe of lipid membranes provides evidence supporting the CSS coating of plasma-treated PCL fibers. Further, anti-CD20 antibodies are used as a model protein to evaluate the potential of lipid-mediated protein immobilization as a mechanism to functionalize the CSS-PCL fiber scaffolds. Upon anti-CD20 functionalization, the CSS-PCL fiber scaffolds capture Granta-22 cells 2.4 times more than the PCL control does, although the two fiber scaffolds immobilize a comparable amount of anti-CD20. Taken together, results from the present study demonstrate that the CSS coating and CSS-mediated antibody immobilization offers an appealing strategy to functionalize electrospun synthetic polymer fibers and confer cell-specific functions on the fiber scaffolds, which can be mechanically robust but often lack biological functions.

Hollow magnetic microspherules from along the lower Younger Dryas boundary (c. 12.9 ka bp) in New Mexico (USA) were studied using scanning electron microscopy, electron probe microanalysis, X‐ray d...

The crystal structure of brackebuschite, ideally Pb2Mn3+(VO4)2(OH), was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant lowering of the reliability factors., The crystal structure of brackebuschite, ideally Pb2Mn3+(VO4)2(OH) [dilead(II) manganese(III) vanadate(V) hydroxide], was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant improvement of accuracy and an unambiguous hydrogen-bonding scheme. Brackebuschite belongs to the brackebuschite group of minerals with general formula A 2 M(T1O4)(T2O4)(OH, H2O), with A = Pb2+, Ba, Ca, Sr; M = Cu2+, Zn, Fe2+, Fe3+, Mn3+, Al; T1 = As5+, P, V5+; and T2 = As5+, P, V5+, S6+. The crystal structure of brackebuschite is based on a cubic closest-packed array of O and Pb atoms with infinite chains of edge-sharing [Mn3+O6] octa­hedra located about inversion centres and decorated by two unique VO4 tetra­hedra (each located on a special position 2e, site symmetry m). One type of VO4 tetra­hedra is linked with the 1 ∞[MnO4/2O2/1] chain by one common vertex, alternating with H atoms along the chain, while the other type of VO4 tetra­hedra link two adjacent octa­hedra by sharing two vertices with them and thereby participating in the formation of a three-membered Mn2V ring between the central atoms. The 1 ∞[Mn3+(VO4)2OH] chains run parallel to [010] and are held together by two types of irregular [PbOx] polyhedra (x = 8, 11), both located on special position 2e (site symmetry m). The magnitude of the libration component of the O atoms of the 1 ∞[Mn3+(VO4)2OH] chain increases linearly with the distance from the centerline of the chain, indicating a significant twisting to and fro of the chain along [010]. The hy­droxy group bridges one Pb2+ cation with two Mn3+ cations and forms an almost linear hydrogen bond with a vanadate group of a neighbouring chain. The O⋯O distance of this inter­action determined from the structure refinement agrees well with Raman spectroscopic data.

The crystal structure of tetra­wickmanite, a tetra­gonal hydroxide-perovskite mineral, has been determined for the first time by means of single-crystal X-ray diffraction. It is characterized by alternating corner-linked [Mn2+(OH)6] and [Sn4+(OH)6] octa­hedra whose sense of rotation varies along c, in contrast to its dimorph, the cubic wickmanite., The crystal structure of tetra­wickmanite, ideally Mn2+Sn4+(OH)6 [mangan­ese(II) tin(IV) hexa­hydroxide], has been determined based on single-crystal X-ray diffraction data collected from a natural sample from Långban, Sweden. Tetra­wickmanite belongs to the octa­hedral-framework group of hydroxide-perovskite minerals, described by the general formula BB’(OH)6 with a perovskite derivative structure. The structure differs from that of an ABO3 perovskite in that the A site is empty while each O atom is bonded to an H atom. The perovskite B-type cations split into ordered B and B′ sites, which are occupied by Mn2+ and Sn4+, respectively. Tetra­wickmanite exhibits tetra­gonal symmetry and is topologically similar to its cubic polymorph, wickmanite. The tetra­wickmanite structure is characterized by a framework of alternating corner-linked [Mn2+(OH)6] and [Sn4+(OH)6] octa­hedra, both with point-group symmetry -1. Four of the five distinct H atoms in the structure are statistically disordered. The vacant A site is in a cavity in the centre of a distorted cube formed by eight octa­hedra at the corners. However, the hydrogen-atom positions and their hydrogen bonds are not equivalent in every cavity, resulting in two distinct environments. One of the cavities contains a ring of four hydrogen bonds, similar to that found in wickmanite, while the other cavity is more distorted and forms crankshaft-type chains of hydrogen bonds, as previously proposed for tetra­gonal stottite, Fe2+Ge4+(OH)6.

The crystal structure of a natural specimen of Tetrawickmanite (Langban, Sweden) with the ideal composition of Mn2+Sn4+(OH)6 (tetragonal space group P42/n, Z = 4, single crystal XRD) belongs to the octahedral-framework group of hydroxide-perovskite minerals described by the general formula BB′(OH)6.

Calcioferrite, ideally Ca4MgFe3+4(PO4)6(OH)4·12H2O (tetracalcium magnesium tetrairon(III) hexakis-phosphate tetrahydroxide dodecahydrate), is a member of the calcioferrite group of hydrated calcium phosphate minerals with the general formula Ca4AB4(PO4)6(OH)4·12H2O, whereA= Mg, Fe2+, Mn2+andB= Al, Fe3+. Calcioferrite and the other three known members of the group, montgomeryite (A= Mg,B= Al), kingsmountite (A= Fe2+,B= Al), and zodacite (A= Mn2+,B= Fe3+), usually occur as very small crystals, making their structure refinements by conventional single-crystal X-ray diffraction challenging. This study presents the first structure determination of calcioferrite with composition (Ca3.94Sr0.06)Mg1.01(Fe2.93Al1.07)(PO4)6(OH)4·12H2O based on single-crystal X-ray diffraction data collected from a natural sample from the Moculta quarry in Angaston, Australia. Calcioferrite is isostructural with montgomeryite, the only member of the group with a reported structure. The calcioferrite structure is characterized by (Fe/Al)O6octahedra (site symmetries 2 and -1) sharing corners (OH) to form chains running parallel to [101]. These chains are linked together by PO4tetrahedra (site symmetries 2 and 1), forming [(Fe/Al)3(PO4)3(OH)2] layers stacking along [010], which are connected by (Ca/Sr)2+cations (site symmetry 2) and Mg2+cations (site symmetry 2; half-occupation). Hydrogen-bonding interactions involving the water molecules (one of which is equally disordered over two positions) and OH function are also present between these layers. The relatively weaker bonds between the layers account for the cleavage of the mineral parallel to (010).

Aqueous solutions of methylene blue sealed in glass ampoules have been exposed to γ-radiation, stored at different temperatures and checked periodically for dye retention for a period of 2 months. The results obtained show that the dye destruction proceeds after irradiation and at a rate dependent on the storage temperature. Parallel tests conducted with non-irradiated samples show small losses of dye, of the order of the experimental error. Another set of experiments using electron beams revealed no practical differences in the extent of dye destruction when the temperature during the irradiation process was varied from 45 to 150°F. Some practical recommendations are given in order to attain a good degree of reproductibility when using the methylene blue as a radiation dosimeter. In summary also, it may be stated that this dosimeter is of value for routine evaluation of electron and γ-ray beams for: 1. (1) It has a first order dose response which is linear to at least 6 × 10 6 rep (using a 1000 mcg/ml solution from 1 × 10 6 to 6 × 10 6 rep). 2. (2) It is easily measured using common laboratory colorimeters. 3. (3) It is temperature independent above the freezing point of water. 4. (4) It is stable for 1 week at refrigerator temperatures.