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The ab initio crystal structure solution of a layer silicate is presented. Since the crystallinity of the material is limited, the corresponding X-ray powder pattern shows only moderate resolution. Based on a new interpretation of the tangent formula, a general direct method strategy for the determination of the crystal structure of poorly crystalline materials from X-ray powder patterns is presented. The structure model derived from the interpretation of the E map was subsequently refined with the Rietveld technique using the whole diffraction pattern. This leads finally to a picture of the crystal structure of atomic resolution which explains in full detail the specific characteristics of the material.

29Si MAS NMR spectra of natural melanophlogite as well as of synthetic melanophlogite indicate that the room temperature lattice structure has lower symmetry than expected from its proposed crystal structure. On heating the samples to temperatures above room temperature, the structure undergoes a reversible phase transition with a transition temperature characteristic of the locality. For the synthetic melanophlogite, the transition is over the range 298 K to 338 K. From low temperature NMR spectra it is concluded that the low temperature forms of synthetic melanophlogite and of melanophlogite from Sicily differ in their crystal lattice symmetries due to their characteristic guest species.

A new porous tectosilicate has been synthesized in the presence of boric acid and 1, 2, 2, 6, 6-pentamethylpiperidine as guest molecules. It crystallizes in the monoclinic system with ao=9.91 (1) Å, bo=20.62 (3) Å, co=9.80 (2) Å, and ß-99.7 (2)0. After heat treatment at 820°C for 1 hour the guest molecules are set free whereas the silica host framework is retained. From crystal morphology and thermal behaviour it is concluded that the new material possesses channel-like voids.

Nonasils-[4158], 88SiO2·8M8·8M9·4M20, have been synthesized with 2-methylpyrrolidine, hexamethyleneimine, 2-(aminomethyl)-tetrahydrofuran, 1,2-diaminocyclohexane, 2-methylpiperidine, 2-methylpiperazine, 1-aminobutane, 2-aminobutane, and 2-aminopentane as guest molecules, M20. The samples have been prepared from aqueous silicate solutions which were sealed in silica tubes and heated at about 200°C for several weeks. These clathrasils crystallize in space groupFmmm. For the nonasil with 2-aminopentane as the guest molecule and the unit cell dimensionsao=22.232(6) Å,b0=15.058(4) Å, andco=13.627(4) Å, the structure has been refined using 550 non-equivalent single crystal reflexions to a reliability factorRw=0.125. The 3-dimensional 4-connected silica host framework has three types of cage-like voids, [5464], [4158], and [58612], the latter housing the structure-controlling guest molecules, M20. The non-spherical shape of the guest molecules is the most important factor for the formation of nonasils-[4158]. On heating nonasils-[4158] up to 950°C the organic guest species are driven out and the pure silica form of nonasil is obtained.

Dodecasil 1H, 34SiO2 · 3M12 · 2M12' · 1M20 with M12, M12'=N2 and M20=1-aminoadamantane, is hexagonal witha=13.825(2) Å,c=11.189(2) Å and crystallizes in space groupP6/mmm. With 767 unique reflexions the structure has been refined to a weighted reliability factorRw=0.054. The three-dimensional four-connected host framework is built by corner sharing [SiO4] tetrahedra and shows three types of cagelike voids, [512] cages, [435663] cages and [51268] cages, the latter housing the 1-aminoadamantane guest molecule. Difference Fourier synthesis ?(obs)-?(calc(Si,O)) delineate the guest molecules within the different types of cage. Residual electron densities reveal positional disorder of the 1-aminoadamantane guest molecule. Four crystallographically different preferred orientations for the 1-aminoadamantane guest molecule are found.

We studied carbonates of mainly postmagmatic origin. As a result of extensive measurements of the absorption spectra, light of λ=253 nm of a Xenon lamp was used for excitation. The emitted luminescence was measured by a photometer. Luminescence of considerable intensity is exhibited by calcites, aragonites, smithsonites, strontianites as well as by witherites and cerussites. Calcites have the most strongly differentiated spectrum. Each of their five different luminescence types is caused by a special activation. Particularly characteristic are calcites, whose luminescence is activated (a) by lattice defects and/or Zn-contents (broad emission band with maximum at about 420 nm), (b) by Mn/Pb-substitution (maxima at 325 and 420 nm), (c) by REE (maxima at 340–360, 480, 545, 575, 623 and 670 nm). The other, also luminescing carbonates, show a close relationship to the calcite of the ‘fundamental type’ (a) but with varying position of their emission maxima. Also most of the phosphorescing samples of calcite are of this type (a). The majority of these calcites originate from telethermal, surface-near formation regions and from resolutions, respectively. Fe, Ni, and in the case of smithsonite also Cu, are ‘killing elements’, which are less efficient by REE-activation than by Mn/Pb-activation. In particular phosphorescence and activation by lattice defects will be disturbed. The luminescence analysis represents a possibility for mineral identification. Furthermore it gives criteria for chemical homogenity of minerals, and locates concentrations of certain elements in inhomogeneous samples. For the most important activators it is a tool for qualitative element detection, especially in the case of REE.

The isomer distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils has been shown to correlate to the local mean annual temperature. Here, we explore the use of brGDGT distributions as proxy for the elevation at which soil organic carbon is preferentially mobilized in the Central Himalaya. Soil brGDGT distributions collected along an altitudinal profile, spanning elevations from 200 to 4,450 m asl, are linearly correlated to elevation. We use this calibration to trace the provenance of soil organic matter in suspended sediments of rivers draining the Himalaya. BrGDGT distributions of fluvial sediments reflect the mean elevation of the soil cover in most catchments. Inverse modeling of the brGDGT data set suggests similar relative contribution to soil organic carbon mobilization from different land covers within a factor 2. We conclude that riverine soil organic carbon export in the Himalaya mostly occurs pervasively and is at the catchment scale insensitive to anthropogenic perturbations. Soil degradation influences the global climate and has direct impacts on the ability of soils to deliver economic and ecological services. Identifying the source of eroded soil‐derived carbon entrained in sediments of large rivers remains challenging. In this contribution, we use the temperature‐sensitive signature of soil microbe‐derived organic molecules to trace the source of soil carbon exported in river sediments of the rapidly eroding Central Himalaya of Nepal. Molecular signatures of soils, sampled over a wide range of elevations, and hence temperatures are plotted on an elevation profile. River sediments are then compared to soil signatures in order to identify elevations of preferential soil export through rivers. Our data shows that soil‐derived carbon is sampled uniformly over most of the catchments, indicating that soil export by Himalayan rivers is not driven by localized human perturbations such as agriculture or deforestation. A calibration for soil branched glycerol dialkyl glycerol tetraether (brGDGT) signals against an elevation profile is developedThe provenance of soil organic matter in riverine suspended sediments is traced based on corresponding brGDGT distributionsSoil organic carbon in most river sediments originates from the entire soil‐covered catchment, indicating uniform soil organic matter export