Platy Crystals Research Articles

Growth of single crystals of crowningshieldite (α-NiS) by chemical-vapour transport

Single crystals of crowningshieldite (α-NiS) were synthesized in three runs via chemical-vapour transport (CVT) over a 20 cm horizontal gradient of 700 → 600 °C (No. 1) and 800 → 700 °C (No. 2 & 3) in evacuated fused silica capsules using natural millerite from Coleman mine in Sudbury, Ontario, Canada with the composition (Ni0.976Fe0.013Co0.003)Σ0.992S and I2 as a transport reagent. Products were characterized via PXRD and SEM methods. Resultant crystals are euhedral, 10 to 400 μm in diameter, and occur as three distinct populations: 1) platy crystals exhibiting dominant pinacoid {0001} and minor dipyramid {101¯1}; 2) equant crystals with equal development of both the pinacoid {0001} and dipyramid {101¯1}; and 3) blocky crystals showing only the dipyramid {101¯1}. The largest crystals were produced at higher temperatures, but experiments lasting longer than 12 days did not result in significant additional crystal growth. In addition to euhedral crystals, anhedral droplets were observed to form during run No. 2 & 3 suggesting deposition as a liquid as opposed to solid crystals. Synthesis of crystals from a pure NiS compound as opposed to that of natural composition may improve the quality of the resulting crystals and better constrain the ideal growth temperature.

Gorerite, CaAlFe11O19, a new mineral of the magnetoplumbite group from the Negev Desert, Israel

AbstractGorerite, ideally CaAlFe11O19 is a new mineral and M-type hexaferrite of the magnetoplumbite group. It was found in ferrite-rich segregations of esseneite–gehlenite–wollastonite–anorthite melted rock of the ‘olive’ subunit of pyrometamorphic rocks located near Hatrurim Junction in the Negev Desert, Israel. Within these ferrite-rich segregations up to 100 μm in size, platy crystals of gorerite up to 50 μm in size intergrow with hibonite, hematite, maghemite, magnesioferrite, dorrite, barioferrite and andradite, forming aggregates. Additionally, small crystals of gorerite occur within magnesioferrite. Importantly, gorerite did not crystallise directly from the melt. Instead, it emerged through a reaction involving earlier crystallised hibonite and an iron-enriched melt, resulting in the partial or complete replacement of hibonite by gorerite. Gorerite appears grey in the reflected light (R = 18–23%), displaying distinct bireflectance: dark-grey perpendicular to Z and light-grey parallel to Z. Its Raman spectrum exhibits only one strong band at 700 cm–1, which shifts to higher frequencies with increasing Al content. Gorerite crystallises in the P63/mmc space group, with lattice parameters a = 5.8532(4) Å, c = 22.7730(2) Å and V = 675.67(7) Å3 with Z = 2. It exhibits a structure characterised by an intercalation of triple spinel-like S blocks and rock-salt type R blocks along the hexagonal c-axis.

Enricofrancoite, KNaCaSi4O10, a new Ca–K–Na silicate from Somma–Vesuvius volcano, southern Italy

Abstract Enricofrancoite (IMA2023–002), ideally KNaCaSi4O10, is a new litidionite-group member found as the product of high-temperature alteration of hosting silicates with the enrichment by Cu-bearing fluids at the rock–fumaroles interface related to the 1872 eruption of Somma–Vesuvius volcano, southern Italy. It occurs as euhedral and platy crystals or crusts together with litidionite, tridymite, wollastonite and Al- and Fe-bearing diopside, kamenevite, perovskite, rutile, Ti-rich magnetite and colourless Si-glass. Single crystals of enricofrancoite are transparent colourless or light blue with a vitreous lustre. Mohs hardness is 5.5. Dmeas is 2.63(3) g/cm3 and Dcalc is 2.63 g/cm3. The mineral is optically biaxial (−), α = 1.542(5), β = 1.567(5),γ = 1.575(5); 2V(meas) = 60(2)° and 2Vcalc = 58°. The mean chemical composition (wt.%, electron-microprobe data) is: SiO2 64.81, Al2O3 0.03, TiO2 0.08, FeO 0.07, MgO 1.71, CaO 10.64, CuO 2.22, Na2O 8.56, K2O 11.41, total 99.94. The empirical formula based on 10 O apfu is: K0.90Na1.03(Ca0.71Mg0.16Cu0.10)Σ0.97Si4.02O10. The Raman spectrum contains bands at 133, 248, 265, 290, 335, 400, 438, 510, 600, 690 and 1120 cm–1 and the wavenumbers of the IR absorption bands are: 424, 470, 492, 530, 600, 630, 690, 750, 788, 970, 1040 and 1160 cm–1. The eight strongest lines of the powder X-ray diffraction pattern are [d, Å (I, %) hkl]: 6.75 (42) 01 $\bar{1}$ , 3.65 (20) 11 $\bar{2}$ , 3.370 (100) 02 $\bar{2}$ , 3.210 (52) 102, 3.051 (18) 111, 3.033 (25) 2 $\bar{1}\bar{2}$ , 2.834 (22) 02 $\bar{3}$ and 2.411 (72) 03 $\bar{2}$ . Enricofrancoite is triclinic, space group P $\bar{1}$ , unit-cell parameters refined from the single-crystal data are a = 7.0155(4) Å, b = 8.0721(4) Å, c = 10.0275(4) Å, α = 104.420(4)°, β = 99.764(4)°, γ = 115.126(5)° and V = 472.74(5) Å3. The crystal structure has been refined from single-crystal X-ray diffraction data to R1 = 0.035 on the basis of 2078 independent reflections with Fo > 4σ(Fo). Enricofrancoite is an H2O-free analogue of calcinaksite with 5-coordinated Ca2+ at the M site.

Plumbogaidonnayite, PbZrSi3O9⋅2H2O, a new Pb-member of the gaidonnayite group from the Saima alkaline complex, Liaoning Province, China

AbstractPlumbogaidonnayite, ideally PbZrSi3O9⋅2H2O, is a new gaidonnayite-group mineral discovered as a secondary product derived from the alteration of eudialyte from the Saima alkaline complex, China. It occurs as aggregates (up to 1 mm) composed of subhedral to anhedral or platy crystals (individually 5–50 μm), associated closely with microcline, natrolite, aegirine, gaidonnayite, georgechaoite, zircon, bobtraillite and britholite-(Ce) in eudialyte pseudomorphs. The crystals are transparent, colourless or light brown with a vitreous lustre. Plumbogaidonnayite is brittle with conchoidal fracture, and it has a Mohs hardness of ~5 and a calculated density of 3.264 g/cm3. It is optically biaxial (+) with α = 1.61(3), β = 1.63(3) and γ = 1.66(4). The calculated 2V is 80°, with the optical orientations X, Y and Z parallel to the crystallographic a, b and c axes, respectively. The empirical formula is (Pb0.70Ca0.17Ba0.01K0.11Na0.01Y0.01)Σ1.01(Zr1.00Hf0.01Ti0.01)Σ1.02Si3.01O9⋅2H2O calculated on the basis of nine oxygen atoms per formula unit and assuming the occurrence of two H2O groups. Plumbogaidonnayite is orthorhombic, P21nb, a = 11.7690(4) Å, b = 12.9867(3) Å, c = 6.66165(16) Å, V = 1018.17(5) Å3 and Z = 4. The nine strongest lines of its powder XRD pattern [d in Å (I, %) (hkl)] are: 6.489 (36) (020), 5.803 (100) (101), 4.661 (27) (021), 4.336 (29) (121), 3.640 (30) (221), 3.114 (79) (112), 2.947 (27) (400), 2.622 (27) (241) and 2.493 (27) (312). Plumbogaidonnayite has a similar spiral chain framework structure with gaidonnayite and georgechaoite, which is composed of SiO4 tetrahedra and ZrO6 octahedra, but with disordered extra-framework sites (cations and H2O groups) characterised by the substitution of 2Na+ (K+)→Pb2+ (Ca2+) + □ (vacancy). The discovery of plumbogaidonnayite adds a new perspective on the cation ordering and heterovalent substitution mechanism in gaidonnayite-group minerals.

Virgilluethite: A New Mineral and the Natural Analogue of Synthetic β-MoO3·H2O, from Cookes Peak, Luna County, New Mexico, USA

Abstract The new mineral virgilluethite, ideally β-MoO3·H2O, was discovered in an unnamed short adit on the Summit group of claims near Cookes Peak, Luna County, New Mexico, USA. All virgilluethite crystals are pseudomorphs after sidwillite and occur as aggregates of sub-parallel platy crystals. Associated minerals include sidwillite, raydemarkite, tianhuixinite, ilsemannite, jordisite, powellite, fluorite, baryte, pyrite, and quartz. Virgilluethite is pale yellow-green in transmitted light, transparent with white streak and vitreous luster. It is flexible with a Mohs hardness of ∼2; cleavage is perfect on {010}. No twinning was observed visually. The measured and calculated densities are 3.71(5) and 3.69 g/cm3, respectively. Virgilluethite is insoluble in water or hydrochloric acid. An electron probe microanalysis yielded an empirical formula (Mo1.00)O3·H2O based on 4 O apfu. Virgilluethite is the natural analogue of the β-form of MoO3·H2O, which was first synthesized over a century ago (Rosenheim & Davidsohn 1903). It is monoclinic, space group P21/c, with unit-cell parameters a = 7.2834(3), b = 10.6949(6), c = 7.4861(3) Å, β = 112.779(2)°, V = 583.03(5) Å3, and Z = 4. The crystal structure of virgilluethite, which is topologically identical to that of tungstite (WO3·H2O), is characterized by highly distorted and elongated MoO5(H2O) octahedra that share four corners in the equatorial plane with one another to form sheets parallel to (010). These sheets, analogous to those in sidwillite, are held together by H-bonding between the H2O molecule and the O atom in the axial position in the adjacent sheets. Virgilluethite and raydemarkite are dimorphs of MoO3·H2O. Unlike virgilluethite, the MoO6 octahedra in raydemarkite share edges to form isolated double chains, resembling those found in zhenruite, (MoO3)2·H2O.

Mikenewite, the natural analogue of synthetic α-Mn2+(S4+O3)⋅3H2O, a new sulfite mineral from the Ojuela mine, Mapimí, Mexico

AbstractA new mineral species, mikenewite (IMA2022-102), ideally Mn2+(S4+O3)⋅3H2O, has been discovered from the San Judas Chimney, Ojuela mine, Mapimí, Durango, Mexico. It occurs as spheres of platy crystals. Associated minerals include goethite, cryptomelane, adamite and lotharmeyerite. Mikenewite is yellowish in transmitted light, transparent with a white streak and vitreous lustre. It is brittle and has a Mohs hardness of 2½–3. Cleavage is perfect on {101}. The measured and calculated densities are 2.48(5) and 2.467 g/cm3, respectively. Optically, mikenewite is biaxial (+), with α = 1.606(5), β = 1.614(5), γ = 1.627(1) (white light), 2V(meas.) = 69(3)° and 2V(calc.) = 77°. An electron microprobe analysis yielded an empirical formula (based on 6 O apfu) of (Mn0.86Zn0.12Fe0.04Ca0.02)Σ1.04(S0.98O3)⋅3H2O, which can be simplified to (Mn,Zn,Fe)(SO3)⋅3H2O.Mikenewite is the natural analogue of synthetic α-Mn2+(S4+O3)⋅3H2O, as well as the Mn-analogue of albertiniite, Fe2+(S4+O3)⋅3H2O. It is monoclinic, with space group P21/n and unit-cell parameters a = 6.6390(3), b = 8.8895(4), c = 8.7900(4) Å, β = 96.095(2)°, V = 515.83(4) Å3 and Z = 4. The crystal structure of mikenewite is characterised by each Mn atom coordinated octahedrally by six O atoms, three from different sulfite O atoms and three from H2O molecules. Each S4+O3 group is bonded to three Mn atoms, resulting in a sheet parallel to (101) with the sheet composition of Mn2+(S4+O3)⋅3H2O. Such sheets, stacked along [10$\bar{1}$], are joined together by hydrogen bonds, accounting for the perfect cleavage of the mineral. Mikenewite is dimorphous with orthorhombic Pnma gravegliaite, as albertiniite is with fleisstalite. Its discovery from the Ojuela mine, which is particularly rich in Zn, implies the possibility of finding Zn-bearing sulfites there as well.

Design and mechanism of agglomeration of aspirin crystals in pure solvents

Agglomeration with improved flowability for platy crystals is desirable in pharmaceutical downstream processing. The formation of agglomerates in pure solvents without the aid of bridging liquids is a convenient and low-cost method compared with complex spherical crystallization. In this work, the adhesion free energies between aspirin crystals in six solvents were calculated using Lifshitz-van der Waals acid-base theory to screen suitable solvents for agglomeration. The maximum stirring rate for agglomeration was determined by adhesion forces and dispersion forces. Then the agglomerates of plate-shaped aspirin were successfully prepared in acetone, methanol, ethanol, 2-propanol, and ethylene glycol without additives by simple cooling crystallization. The interactions between solvent and crystal surfaces were also used to explain the outcomes. A feasible mechanism for the agglomeration process of platy crystals was elucidated, involving the adhesion of dominant crystal facets at the beginning. The effect of stirring rate, cooling rate, and initial supersaturation on agglomeration degree and particle size of aspirin agglomerates were studied. The obtained aspirin agglomerates under the optimal conditions exhibited a uniform particle size distribution, a high agglomeration degree, and superior flowability.

Gysinite-(La), PbLa(CO3)2(OH)⋅H2O, a new rare earth mineral of the ancylite group from the Saima alkaline complex, Liaoning Province, China

AbstractThe new mineral, gysinite-(La), with the ideal formula PbLa(CO3)2(OH)⋅H2O, has been discovered in lujavrite from the Saima alkaline complex, Liaoning Province, China. It commonly occurs as subhedral to anhedral, granular and platy crystals of 5 to 50 μm in size, in interstices or enclosed in microcline, aegirine and nepheline. Associated minerals include nepheline, aegirine, microcline, natrolite, eudialyte, lamprophyllite, bastnäsite-(Ce), parasite-(Ce), ancylite-(La), ancylite-(Ce), bobtraillite, britholite-(Ce), thorite, calcite and galena. The crystallisation of gysinite-(La) may be related to the post-magmatic carbonation event. Gysinite-(La) crystals are generally transparent, colourless, or pale yellow, with a vitreous lustre and white streak. It is brittle with an uneven fracture, and the estimated Mohs hardness is 3½ to 4. The calculated density is 5.007 g/cm3. Optically, gysinite-(La) is biaxial (–), α= 1.832(2), β= 1.849(4), γ = 1.862(5) in white light and 2Vmeas = 81.6°. The empirical formula of gysinite-(La) is (La0.93Pb0.61Nd0.23Pr0.14Sr0.04Gd0.02Sm0.01Eu0.01Ca0.01)Σ2(CO3)2(OH)1.34⋅0.66H2O, which is calculated on the basis of general formula (REExM2+2–x)(CO3)2(OH)x⋅(2–x)H2O. The strongest eight lines of its powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 5.596 (21) (011), 4.349 (100) (110), 3.732 (68) (111), 2.984 (61) (121), 2.667 (21) (031), 2.363 (48) (131), 2.090 (29) (221) and 2.028 (21) (212). Gysinite-(La) is orthorhombic, in the space group Pmcn, and unit-cell parameters refined from single-crystal X-ray diffraction data are: a = 5.0655(2) Å, b = 8.5990(3) Å, c = 7.3901(4) Å, V = 321.90(2) Å3 and Z = 2. It is a new member of the ancylite group and isostructural with gysinite-(Nd), but with La and Pb dominant in the metal cation sites in the structure.

Fluorsigaiite, Ca2Sr3(PO4)3F, a new mineral of the apatite supergroup from the Saima alkaline complex, Liaoning Province, China

AbstractFluorsigaiite, ideally Ca2Sr3(PO4)3F, is a new Sr analogue of fluorphosphohedyphane and a new member of the apatite supergroup. It was discovered in lujavrite from the Saima alkaline complex, Liaoning Province, China. Fluorsigaiite commonly occurs as individual prismatic, columnar and platy crystals of 10 to 50 μm in size, associated with microcline, nepheline, aegirine, natrolite, eudialyte, fluorapatite, a fluorstrophite-like mineral, stronadelphite and calcite. Occasionally, crystals of fluorsigaiite form prismatic aggregates in the interstices of lujavrite. Fluorsigaiite is translucent to transparent, colourless to yellowish white with a vitreous lustre and without fluorescence. The estimated Mohs hardness is 5, and the tenacity is brittle with uneven fractures. The calculated density is 3.842 g/cm3. Optically, fluorsigaiite is uniaxial (–) with ω = 1.64(1) and ɛ = 1.63(1) in white light and without dispersion. The mean chemical composition (in wt.%) of fluorsigaiite is Na2O 0.75, CaO 15.17, SrO 44.44, La2O3 3.64, Ce2O3 2.22, Pr2O3 0.19, Nd2O3 0.13, Sm2O3 0.05, Gd2O3 0.23, P2O5 31.87, F 1.91, H2O 0.46, sum 100.26, giving the empirical formula (Sr2.82Ca1.79Na0.16La0.15Ce0.09Pr0.01Nd0.01Gd0.01)Σ5.04P2.97O12[F0.66(OH)0.34]Σ1, which is calculated on the basis of 13 total anions and F+(OH) = 1. The strongest eight lines of its powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.563 (15) (002), 3.275 (15) (102), 3.144 (19) (120), 2.876 (100) (121), 2.861 (96) (112), 2.772 (27) (300), 1.991 (17) (222) and 1.895 (23) (213). Fluorsigaiite is hexagonal, in the space group P63/m and unit-cell parameters refined from single-crystal X-ray diffraction data are: a = 9.6101(2) Å, c = 7.1311(1) Å, V = 570.35(3) Å3 and Z = 2. It is isostructural with hedyphane-group minerals, and contains different prevailing (species-defining) Ca and Sr cations at the Ca1 and Ca2 sites, respectively. Fluorsigaiite was probably formed from Sr-rich fluids at late-magmatic or hydrothermal stage of the Saima lujavrite.

Petrographic and geochemical constraints on the formation of gravity‐defying speleothems

AbstractCave carbonates, seemingly growing in defiance of gravity, have attracted the community's interest for more than a century. This paper focusses on ‘helictites’, contorted vermiform speleothems with central capillaries. Petrographic, crystallographic and geochemical data of calcitic and aragonitic helictites (recent to 347 ka) from three caves in Western Germany are placed in context with previous work. Aragonitic helictites from one site, the Windloch Cave, form exceptionally large and complex structures that share similarities with the celebrated helictite arrays in the Asperge Cave in France. Aragonitic and calcitic helictites differ significantly in their crystal fabrics and internal geometry. Calcitic helictites are best described as a composite crystal fabric consisting of fibrous mesocrystals. Aragonite helictites display a complex fabric of acicular to platy crystals, some of which show evidence for growth‐twinning and perhaps crystallisation via a monoclinal precursor stage. The micro‐tomographic characterisation of several orders of channels and their complex architecture raises important questions regarding fluid migration and helictite architecture. In terms of their isotope geochemistry, helictites are depleted in 13C to various degrees, isotope values that are controlled by the mixing of fluids and mineralogy‐related fractionation. Regarding their δ18O values, most helictites overlap with other calcitic and aragonitic speleothems. Previous models explaining the twisted morphology of helictites are discussed from the viewpoint of fluid migration and CO2 degassing rates, mineralogy and helictite petrography. For the complex aragonitic helicities documented here, the most likely mechanisms to explain the contorted growth forms include the internal capillary network combined with localised (sector) growth at the helictite tip. The morphologically simpler calcitic helictites are best explained by capillary and surface flow. Future work should include geomicrobiology to assess the significance of induced mineralisation and transmission electron microscopy analysis to more quantitatively assign crystallographic properties.

The Crystal Structure of Malhmoodite from Custer, South Dakota, USA

ABSTRACT An occurrence of malhmoodite, Fe2+Zr(PO4)2·4H2O, from the Scott's Rose Quartz mine, Custer County, South Dakota, USA, has been identified. It occurs as divergent groups of yellowish, flat-lying platy crystals on football-size masses of altered löllingite with scorodite, parasymplesite, karibibite, schneiderhöhnite, kahlerite, and zircon. An electron probe microanalysis of malhmoodite yielded an empirical formula (based on 12 O apfu) of Fe1.06(Zr1.10Hf0.03)Σ1.13[(P0.93As0.01)Σ0.94O4]2·4H2O. Single-crystal X-ray structure analysis shows that malhmoodite is the Fe-analogue of zigrasite, MgZr(PO4)2·4H2O. Malhmoodite is triclinic with space group P and unit-cell parameters a = 5.31200(10), b = 9.3419(3), c = 9.7062(3) Å, α = 97.6111(13), β = 91.9796(11), γ = 90.3628(12)°, V = 477.10(2) Å3, Z = 2, in contrast to the previously reported monoclinic symmetry with space group P21/c and unit-cell parameters a = 9.12(2), b = 5.42(1), c = 19.17(2) Å, β = 94.8(1)°, V = 944.26 Å3, Z = 4. The crystal structure of malhmoodite is characterized by sheets composed of ZrO6 octahedra sharing all vertices with PO4 tetrahedra. These sheets are parallel to (001) and are joined together by the FeO2(H2O)4 octahedra. The structure determination of malhmoodite, along with that of zigrasite, warrants a re-investigation of synthetic compounds M2+Zr(PO4)2·4H2O (M = Mn, Ni, Co, Cu, or Zn) that have been assumed previously to be monoclinic.

<sup>40</sup>Ar/<sup>39</sup>Ar dating of a hydrothermal pegmatitic buddingtonite–muscovite assemblage from Volyn, Ukraine

Abstract. We determined 40Ar/39Ar ages of buddingtonite, occurring together with muscovite, with the laser-ablation method. This is the first attempt to date the NH4-feldspar buddingtonite, which is typical for sedimentary–diagenetic environments of sediments, rich in organic matter, or in hydrothermal environments, associated with volcanic geyser systems. The sample is a hydrothermal breccia, coming from the Paleoproterozoic pegmatite field of the Korosten Plutonic Complex, Volyn, Ukraine. A detailed characterization by optical methods, electron microprobe analyses, backscattered electron imaging, and IR analyses showed that the buddingtonite consists of euhedral-appearing platy crystals of tens of micrometers wide, 100 or more micrometers in length, which consist of fine-grained fibers of ≤ 1 µm thickness. The crystals are sector and growth zoned in terms of K–NH4–H3O content. The content of K allows for an age determination with the 40Ar/39Ar method, as well as in the accompanying muscovite, intimately intergrown with the buddingtonite. The determinations on muscovite yielded an age of 1491 ± 9 Ma, interpreted as the hydrothermal event forming the breccia. However, buddingtonite apparent ages yielded a range of 563 ± 14 Ma down to 383 ± 12 Ma, which are interpreted as reset ages due to Ar loss of the fibrous buddingtonite crystals during later heating. We conclude that buddingtonite is suited for 40Ar/39Ar age determinations as a supplementary method, together with other methods and minerals; however, it requires a detailed mineralogical characterization, and the ages will likely represent minimum ages.

Collinsit ze železnorudného dolu v Nučicích, nový minerál pro Českou republiku - popis a Ramanova spektroskopie

A very rare phosphate collinsite was found on historical samples of chamosite from the abandoned iron mine Nučice near Prague, Central Bohemia (Czech Republic) located in Ordovician sediments of the Barrandian area. Collinsite forms white to beige radial aggregates up to 15 mm in size composed by platy crystals with pearly lustre. Its chemical composition corresponds to empirical formula: (Ca1.87Sr0.12Ba0.01)Σ2.00(Mg0.57Fe0.41Al0.01)Σ0.99 (PO4)2.00·2H2O (Sr-rich zones) and (Ca1.98Sr0.01)Σ1.99(Mg0.58Fe0.40Al0.01)Σ0.99(PO4)2.00·2H2O (Sr-poor zones). Collinsite is triclinic, space group P-1, unit-cell parameters refined from X-ray powder diffraction data are a 5.734(3), b 6.779(3), c 5.441(2) Å, α 97.33(4)°, β 108.52(3)°, γ 107.25(3)° and V 185.7(1) Å3. Collinsite was found in association with siderite in fissures of chamosite iron ore.

Investigations on the effect of swift heavy silicon ion irradiation on hydroxyapatite

The effect of swift heavy silicon ion irradiation on hydroxyapatite prepared by hydrothermal technique was analyzed. The physical and biological properties were studied using G1XRD, Micro-Raman, photoluminescence, AFM, SEM, EDX, in vitro bioactivity, antimicrobial activity and drug release. When compared with pristine the crystallinity increases with an increase in fluence. Slight reduction in crystallinity was noted for irradiated samples at higher fluence (1×1013 and 1×1014 ions/cm2) than lower fluence (1×1012 ions/cm2). After irradiation the υ4 O-P-O asymmetric bending mode peak at 583 cm−1 disappeared. The PL intensity increases with an increase in fluence and it had become narrow and showed red shift. This suggests the material could find application as phosphors. The enhancement in band gap was attained for irradiated samples than Hpris (5.38–5.5 eV). AFM studies revealed the enhancement of roughness, particle size and pores on irradiation. SEM exposed the creation of pores along with an increase in porosity (2 µm to 30 µm). Formation of platy crystals was noted for 1×1013 ions/cm2 sample. In vitro bioactivity results with the formation of spherical (2 µm) apatite deposition along with the presence of interconnected pores (2–10 µm) which could enhance osteointegration and osteoconduction. In addition, Ca/P ratio was found to increase after soaking in SBF. Initial burst release followed by sustained release was obtained upto 45 h. Therefore it could assist in the treatment of bone and joint infection. Hence, SHI had improved the material to be used in biomedical field as an implant due to its enhanced properties such as crystallinity, pore size, surface roughness, PL intensity, antimicrobial activity, drug release and bioactivity.

Oberwolfachite, SrFe3+3(AsO4)(SO4)(OH)6, a new alunite-supergroup mineral from the Clara mine, Schwarzwald, Germany and Monterniers mine, Rhône, France

AbstractThe new beudantite-group mineral oberwolfachite, ideally SrFe3+3(AsO4)(SO4)(OH)6, was discovered in two localities: Clara mine, Oberwolfach, Schwarzwald, Baden-Württemberg, Germany (holotype) and Monterniers mine, Lantignié, Rhône, Auvergne-Rhône-Alpes, France (cotype). The associated minerals are quartz, baryte, hematite, illite, goethite, beudantite and dussertite (Clara) and arsenogoyazite, jarosite, graulichite-(Ce), goethite and hematite (Monterniers). Oberwolfachite forms yellow to brown platy crystals up to 1 mm across or thick outer zones of mixed (oberwolfachite–beudantite) crystals up to 3 mm across. The lustre is adamantine and the streak is yellow. A distinct cleavage on {0001} is observed. Calculated density is 3.874 g⋅cm–3. The infrared spectra are given. The chemical composition of the holotype/cotype samples are (wt.%, b.d.l. = below detection limit): K2O 1.25/1.86, SrO 6.41/11.15, BaO 8.13/0.45, PbO 2.18/b.d.l., Al2O3 0.16/0.23, Fe2O3 38.99/39.98, La2O3 1.68/not determined, Ce2O3 1.28/2.06, P2O5 0.12/b.d.l., As2O5 17.55/16.55, SO3 12.86/14.99, H2O (calculated) 8.72/9.05, total 99.33/96.62. The empirical formula of the holotype sample is (Sr0.38Ba0.33K0.16Pb0.06La0.06Ce0.05)Σ1.04(Fe3+3.03Al0.02)Σ3.05[(SO4)1.00(AsO4)0.95(PO4)0.01](O6.16H6.00). The crystal structures of both samples were determined using single-crystal X-ray diffraction data and refined to R = 3.13% (holotype, 293 K) and 2.65% (cotype, 170 K). Oberwolfachite is trigonal, R${\bar 3}$m, with a = 7.3270(3) Å, c = 17.0931(9) Å and V = 794.70(8) Å3 (holotype), and a = 7.298(2) Å, c = 16.908(3) Å and V = 779.8(4) Å3 (cotype); Z = 3. The strongest lines of the powder X-ray diffraction pattern of holotype [d, Å (I, %)(hkl)] are: 5.95 (56)(101), 3.664 (37)(110), 3.117 (16)(021), 3.082 (100)(113), 2.548 (15)(024), 2.280 (22)(107), 1.983 (26)(303) and 1.832 (19)(220).

Liudongshengite, Zn4Cr2(OH)12(CO3)·3H2O, a new mineral of the hydrotalcite supergroup, from the 79 mine, Gila County, Arizona, USA

ABSTRACTA new mineral species, liudongshengite, ideally Zn4Cr2(OH)12(CO3)·3H2O, has been found in the 79 mine, Gila County, Arizona, USA. It occurs as micaceous aggregates or hexagonal platy crystals (up to 0.10 × 0.10 × 0.01 mm). The mineral is pinkish and transparent with white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼1.5, with perfect cleavage on (001). No twinning or parting is observed macroscopically. The measured and calculated densities are 2.95 (3) and 3.00 g/cm3, respectively. Optically, liudongshengite is uniaxial (−), with ω = 1.720 (8), ε = 1.660 (7) (white light). An electron microprobe analysis, combined with the carbon content measured using an elemental combustion system equipped with mass spectrometry, yielded the empirical formula (Zn3.25Mg0.17Cr2.58)Σ6.00(OH)12(CO3)1.29·3H2O, based on (M2+ + M3+) = 6 apfu, where M2+ and M3+ are divalent and trivalent cations, respectively.Liudongshengite belongs to the quintinite group within the hydrotalcite supergroup and is the Cr-analogue of zaccagnaite-3R, Zn4Al2(OH)12(CO3)·3H2O. It is trigonal, with space group Rm and unit-cell parameters a = 3.1111(4), c = 22.682(3) Å, and V = 190.12(4) Å3. The crystal structure of liudongshengite is composed of positively charged brucite-like layers, [M2+1–xM3+x(OH)2]x+, alternating with negatively charged layers of (CO3)2–·3H2O. Compared to other minerals in the quintinite group, liudongshengite is remarkably enriched in M3+, with an M2+:M3+ ratio of 1.33:1. Like zaccagnaite-3R and many other hydrotalcite-type minerals, liudongshengite may also possess polytypes, as a series of synthetic hydrotalcite-type compounds with a general chemical formula [Zn4Cr2(OH)12]X2·4H2O, where X = Cl–, NO3–, or ½ SO42–, but with unit-cell parameters different from those for liudongshengite, have been reported previously.

Effects of Heating Rate on the Thermal and Mechanical Properties of the Bauxite-Based Low-Cement Refractory Castables

This study was conducted to investigate the effects of sintering conditions on the phase composition, microstructure, and physico-mechanical properties of the bauxite-based low-cement refractory castables. For this purpose, the specimens were sintered at various temperatures (1350-1450 °C) and heating rates (3-10 °C/min). Results showed that the sintering conditions have a remarkable effect on the physico-mechanical properties of the refractory castables. The mechanical strength was considerably increased by increasing the heating rate from 3 to 10 °C/min which was attributed to lower amounts of porosity and higher amount of the platy crystals of CA6 phase. The lower porosity of the specimens sintered at lower temperature with 10 °C/min of heating rate also resulted in the higher mechanical strength. The results obtained in this study showed a negative linear relationship between the cold crushing strength and porosity of the specimens with a high degree of measurement conformity.

Stergiouite, CaZn2(AsO4)2 · 4H2O – a new mineral from the Lavrion Mining District, Greece

Stergiouite is a new mineral from the Plaka area in the northern part of the Lavrion Mining District, Greece. The mineral occurs as clusters of stacked, platy crystals, associated with galena, sphalerite, native arsenic and sulfur. The crystals are white to colorless, with a pearly luster and white streak. No luminescence under ultraviolet (UV) radiation is observed. Stergiouite is brittle and has a Mohs hardness of ~3. Chemical analysis gave As2O5 42.93 wt%; Sb2O5 2.45 wt%; CaO 10.90 wt%; ZnO 29.79 wt%; and H2Ocalc 13.93 wt%, which corresponds to an empirical formula Ca1.02Zn1.91((As0.95Sb0.08)O4)Σ2.03 · 4H2O. The ideal formula is CaZn2(AsO4)2 · 4H2O. Stergiouite is monoclinic, space group Pc, with unit-cell parameters a 9.416(2) A; b 5.300(1) A; c 10.893(2) A; β 91.767(10)°; V 543.36(3) A3; Z = 2. The strongest lines in the Gandolfi X-ray powder pattern [d in A, I/I100, (hkl)] are: 9.406, 100, (100); 4.619, 80, (102), (110); 3.612, 35, (20 $$ \overline{2} $$ ); 3.494, 35, (112); 2.984, 60, (21 $$ \overline{2} $$ ); 2.922, 50, (212); 2.720, 20, (004); and 2.647, 25, (020). The crystal structure was refined based on single-crystal X-ray diffraction data to R1 = 0.046, wR2 = 0.093. The observed mass density of 3.1(2) g cm−3 compares well with the calculated value (3.183 g cm−3). The framework structure of stergiouite is built up by one type of CaO2(H2O)4 octahedron and each two ZnO4 and AsO4 tetrahedra. These polyhedra share common corners to form three- and four-membered rings. A system of hydrogen bonds (O–O range: 2.70–3.02 A) further stabilizes the structure. The crystal structure of stergiouite is closely related to that of phosphophyllite [Fe[6]Zn2[4](PO4)2 · 4H2O] as well as with members of the hopeite [Zn[6]Zn2[4](PO4)2 · 4H2O] group. Stergiouite is named in honour of Vasilis Stergiou (born 1958) in recognition of his contributions to the mineralogy of the Lavrion deposits.

Synthesis of Calcium Phosphate Powders in Nonaqueous Media for Stereolithography 3D Printing

Methods were presented to synthesize tricalcium phosphate Ca3(PO4)2 (TCP), calcium pyrophosphate Ca2P2O7 (CPP), and TCP/CPP composites in nonaqueous media in the temperature range 25–300°C. It was shown that solvo- and ionothermal synthesis methods can give phosphates of complex composition. The phase composition, micromorphology, and particle size distribution of the obtained powders and their evolution during synthesis were described. The synthesis at 110°C while slowly adding ammonium hydrophosphate to a solution of calcium ethylene glycolate in ethylene glycol gives a nanocrystalline β-TCP powder with an average size of aggregates of platy crystals of 150 nm and a distribution width of 50 nm. The morphological characteristics and sinterability of the powders synthesized in solutions in ethylene glycol make them suitable for producing macroporous ceramics by stereolithography 3D printing methods.

Late Holocene to Recent aragonite‐cemented transgressive lag deposits in the Abu Dhabi lagoon and intertidal sabkha

AbstractModern cemented intervals (beachrock, firmgrounds to hardgrounds and concretionary layers) form in the lagoon and intertidal sabkha of Abu Dhabi. Seafloor lithification actively occurs in open, current‐swept channels in low‐lying areas between ooid shoals, in the intertidal zone of the middle lagoon, some centimetres beneath the inner lagoonal seafloor (i.e. within the sediment column) and at the sediment surface the intertidal sabkha. The concept of ‘concretionary sub‐hardgrounds’, i.e. laminar cementation of sediments formed within the sediment column beneath the shallow redox boundary, is introduced and discussed. Based on calibrated radiocarbon ages, seafloor lithification commenced during the Middle to Late Holocene (ca 9000 cal yr bp), and proceeds to the present‐day. Lithification occurs in the context of the actualistic relative sea‐level rise shifting the coastline landward across the extremely low‐angle carbonate ramp. The cemented intervals are interpreted as parasequence boundaries in the sense of ‘marine flooding surfaces’, but in most cases the sedimentary cover overlying the transgressive surface has not yet been deposited. Aragonite, (micritic) calcite and, less commonly, gypsum cements lithify the firmground/hardground intervals. Cements are described and placed into context with their depositional and marine diagenetic environments and characterized by means of scanning electron microscope petrography, cathodoluminescence microscopy and Raman spectroscopy. The morphology of aragonitic cements changes from needle‐shaped forms in lithified decapod burrows of the outer lagoon ooidal shoals to complex columnar, lath and platy crystals in the inner lagoon. Precipitation experiments provide first tentative evidence for the parameters that induce changes in aragonite cement morphology. Data shown here shed light on ancient, formerly aragonite‐cemented seafloors, now altered to diagenetic calcites, but also document the complexity of highly dynamic near coastal depositional environments.