Reticular synthesis and the design of new materials

The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62718/1/nature01650.pd

Scandium minerals in the miaroles of granite at Baveno, Italy

The discovery of bazzite [Be3Sc2Si6O18] in the granites at Baveno, Italy, dates back to 1915, just a few years after the discovery in Norway of thortveitite, the first known scandium mineral (1911). In 1982 two new scandium minerals, cascandite [CaScSi3O8(OH)] and jervisite [NaScSi2O6] were discovered as additional rarities at Baveno. Owing to the increased activity of collectors, a number of additional finds of bazzite have resulted; similarly, other scandium minerals were recognized to be present, among which thortveitite (Orlandi, 1990) and scandiobabingtonite [Ca2FeScSi5O14(OH)] (Orlandi et al., 1998), the former sometimes affording interesting blue, Mn-bearing specimens (Gramaccioli et al., 2000b). On considering all these discoveries, five of the nine scandium minerals known so far occur at Baveno, which is the type locality for four of them. However, scandium phosphates such as kolbeckite [ScPO4·2H2O] and pretulite [ScPO4] which are relatively diffuse in nature are absent. A possible reason for such a situation is linked to the particular process of formation of these minerals at Baveno, which most probably involves disruption of REE/Sc fluoride complexes following the deposition of relatively abundant fluorite and zinnwaldite from the solutions; there is marked similarity with the Norwegian locality of Heftetjærn, Tørdal, where fluorite is common and many of the Sc-bearing species are the same as at Baveno

Adranosite-(Fe), (NH4)4NaFe2(SO4)4Cl(OH)2 a new ammonium sulfate chloride from La Fossa crater, Vulcano, Aeolian Islands, Italy

AustriaAbstractThe new mineral adranosite-(Fe), ideally (NH4)4NaFe2(SO4)4Cl(OH)2, is the Fe3+-analogue of adranosite. It was found on a pyroclastic breccia in two different fumaroles at “La Fossa” crater of Vulcano, Aeolian Islands, Italy, and corresponds to an anthropogenic product previously observed in a burning coal dump at the Anna mine, near Aachen, Germany. The mineral is tetragonal, space group I41/acd (no. 142), with a = 18.261(2), c = 11.562(1) Å, V = 3855.5(7) Å3 (single-crystal data), and Z = 8. The six strongest reflections in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 9.134(100)(020), 4.569(83)(040), 3.047(79)(152), 6.462(36)(220), 3.232(29)(251), and 2.891(11)(004). The average chemical composition of the holotype is (wt.%): Na2O 5.01, Fe2O3 15.77, Al2O3 5.11, K2O 0.82, (NH4)2O 15.76, SO3 50.96, Cl 3.71, H2O 2.75, –O≡Cl –0.84, total 99.05; the corresponding empirical formula is: [(NH4)3.89K0.11]Σ4.00Na1.04[Fe1.27Al0.64]Σ1.91S4.10O16.40Cl0.67(OH)1.96. Adranosite-(Fe) forms aggregates of pale yellow acicular crystals up to 1 mm in length, the most common forms most probably being {100}, {110}, and {111}. The measured density is 2.18(1) g/cm3, and the calculated density is 2.195 g/cm3. Adranosite-(Fe) is uniaxial (–) with ω = 1.58(1), ε = 1.57(1) (l = 589 nm). Using single-crystal X-ray diffraction data from the holotype, the structure was refined to a final R(F) = 0.0415 for 670 independent observed reflections [I > 2σ(I)]. Adranosite-(Fe) is isostructural with its Al-analogue adranosite and contains NaO4Cl2 square tetragonal bipyramids, linked through their opposite Cl corners and helicoidal chains with composition [FeO4(OH)2SO4]n, both extending along [001]. The framework resulting from the sharing of the sulfate ions between the different chains displays cages in which the nine-coordinated hydrogen-bonded NH4+ ions are hosted

Coexisting calderite and spessartine garnets in eclogite-facies Mn-rich metasediments of the Western Alps

International audienceThe coexistence of a colourless and a yellow garnet was observed in eclogite-facies manganese concentrations of the Mesozoic ophiolitic Zermatt-Saas Unit, at the Praborna mine near Saint-Marcel, Val d'Aoste, Italy, and in the upper Maurienne Valley, France. They occur both in oxidised metachert with hematite and braunite (þ minor Mn-pyroxenoid and tirodite, rare tiragalloite; with ardennite or piemontite in distinct layers), and in more reduced, carbonate-rich boudins included in it. The cooccurrence takes a variety of textural aspects, from coexisting euhedral garnets (10-100 mm in size for the calderite to mm-size for spessartine) to sharp overgrowths of yellow calderitic garnet on colourless spessartine, to yellow cauliflower-like masses (a few hundreds of mm in size) overgrowing colourless spessartine and showing evidence of oscillatory zoning, resorption stages and resumed growth. Sector zoning and anisotropy are common, although not consistent features. Compositions can be expressed to 95% in the quadrilateral system (Ca, Mn 2þ) 3 (Al, Fe 3þ) 2 Si 3 O 12 , with less than 1.0 wt% MgO and 0.8 wt% TiO 2 in colourless spessartine, and less than 0.2 wt% MgO and 1.6 wt% TiO 2 in yellow garnet. Calcium partitions into the ferric garnet. Coexisting pairs define two compositional gaps, bounded by values of the Fe 3þ =(Al þ Fe 3þ) ratio of 10 and 15% for the first one, of 40 and 65% for the other. The optically obvious discontinuity (colour change and Becke's line) corresponds to the narrower gap, between colourless spessartine and yellow spessartine, whereas the broad compositional gap occurs within yellow garnet, between yellow spessartine and yellow calderite, and is only revealed by back-scattered electron images. Only the latter can be a candidate for a miscibility gap, if any