Gyrolite: its crystal structure and crystal chemistry

Abstract The crystal structure of gyrolite from Qarusait, Greenland, was solved and refined with the space group pI and cell parameters a = 9.74(1), b = 9.74(1), c = 22.40(2) A, ex = 95.7(1t, fJ = 91.5(lt, y = l20.0(lt. The structure is built up by the stacking of the structural units already found in the crystal structure ofreyerite Successive complex layers with composition [Ca14Si23Al06o(OH)s]-5 are connected through an interlayer sheet made up by calcium and sodium cations and water molecules. The unit cell content NaCa16Si23Al06o(OHjg' 14H20, determined by the structural study, was confirmed by a chemical analysis, apart from the indication of a somewhat larger water content. The crystal chemistry of gyrolite is discussed on the basis of the present structural results and the chemical data given in the literature for gyrolite from different localities: the crystal chemical formula which accounts for most gyrolite samples is Ca16Si2406o(OHjg '(14+x)H20, with 0~x~3. Stacking disorder, twinning and polytypic variants in gyrolite, as well as the structural relationships of gyrolite with truscottite, reyerite, fedorite and the synthetic phases K and Z are described and discussed

The Crystal Structure of Tobermorite 14 Å (Plombierite), a C-S-H phase

The crystal structure of tobermorite 14 Å (plombierite) was solved by means of the application of the order-disorder (OD) theory and was refined through synchrotron radiation diffraction data. Two polytypes were detected within one very small crystal from Crestmore, together with possibly disordered sequences of layers, giving diffuse streaks along c*. Only one of the two polytypes, could be refined: it has B11b space group symmetry and cell parameters a = 6.735(2) Å, b = 7.425(2) Å, c = 27.987(5) A, γ = 123.25(1)° . The refinement converged to R = 0.152 for 1291 reflections with F 0>4σ(F 0). The characteristic reflections of the other polytype, F2dd space group, a ≈11.2 Å, b ≈ 7.3 Å, c ≈ 56 Å, were recognized but they were too weak and diffuse to be used in a structure refinement. The structure of tobermorite 14 Å is built up of complex layers, formed by sheets of sevenfold coordinated calcium cations, flanked on both sides by wollastonite-like chains. The space between two complex layers contains additional calcium cations and H 2O molecules; their distribution, as well as the system of hydrogen bonds, are presented and discussed. The crystal chemical formula indicated by the structural results is Ca 5Si 6O 16(OH) 2 ·7H 2O

Civil society’s perception of forest ecosystem services. A case study in the Western Alps

Forest Ecosystem Services (FES) are widely recognised by the society nowadays. However, no study in the literature has analysed a ranking of FES after the pandemic. This paper investigated civil society’s perception and knowledge toward these services; in addition, the presence of attitudinal or behavioural patterns regarding individual’s preference, was assessed. A choice experiment was conducted using the Best-Worst Scaling (BWS) method on a sample of 479 individuals intercepted in the Argentera Valley, in the Western Italian Alps. Results, showed a strong interest in biodiversity, aesthetic landscape quality and psychophysical health and a lower interest in provisioning services. Based on the individual preferences, civil society was clustered into five groups for FES, named “Hedonistic,” “Individualist with cultural and health interests,” “Sensitive to regulatory and utilitarian functions,” “Climate change sensitive” and “Livelihood and hedonistic wellbeing.” In general, there was a growing appreciation by civil society for the intangible services offered by the forest, driven by modern lifestyles and an interest in learning more about the provided services. Based on these elements, we believe that similar research should be extended to other mountain contexts to validate the results or to find new insights, and that it is now necessary to study how to involve civil society in decision-making processes of forest planning and management at a local level

Crystal structure of afghanite, the eight-layer member of the cancrinite-group: Evidence for long-range Si,Al ordering

Afghanite, ideally [(Na,K)(22)Ca-10][Si24Al24O96](SO4)(6)Cl-6, is the eight-layer member of the cancrinite-group (ABABACAC stacking sequence). Its structure was refined in the P31c space group to R = 4.5% by means of single-crystal X-ray diffraction data. The cell parameters are a = 12.8013(7) Angstrom, c = 21.4119(18) Angstrom. The P6(3)mc space group proposed in a previous structure refinement is not consistent with the ordered Si,AI pattern suggested by an Si/Al ratio equal to 1 shown by afghanite and other members of the cancrinite-group. The Si-O and Al-O bond distances, 1.61(2) Angstrom and 1.72(2) Angstrom respectively, found in the structure refinement, are in accordance with an ordered Si,AI distribution which is allowed by the P31c space group, a maximal non isomorphic subgroup of P6(3)mc. Afghanite contains six 11-hedra (cancrinite) cages and two 23-hedra (liottite) cages. Four cancrinite cages are stacked along [0 0 z]. They contain a regular....Ca-Cl-Ca-Cl.... chain similar to that observed in davyne and related phases: in particular Ca is located near the center of the bases whereas Cl is near the center of the cage. A liottite cage with a base-sharing cancrinite cage is stacked along [2/3 1/3 z] and [1/3 2/3 z]. The liottite cage hosts a maximum of three sulphate groups which alternate regularly with cation-containing planes. The cancrinite cage, that shares the bases with the liottite cages, presents a disordered distribution of Cl and F reading to two possible configurations similar to those observed in liottite

Thermal behaviour of Al-rich tobermorite

The tobermorite supergroup is composed by a number of calcium-silicate-hydrate (C-S-H) minerals characterized by different hydration states and sub-cell symmetries. Taking into account their basal spacing, closely related to the hydration state, phases having a 14 Å (plombierite), 11 Å (tobermorite, kenotobermorite, and clinotobermorite), and 9 Å (riversideite) basal spacing have been described. Tobermorite and kenotobermorite belong to the so-called tobermorite group and differ for their thermal behaviour which can be "normal" (the phase shrinks to a 9 Å phase at 300 °C) or "anomalous" (the phase preserves its 11 Å basal spacing at 300 °C). Specimens of Al-rich tobermorite from Montalto di Castro and Vallerano, Latium, Central Italy, showing a "normal" thermal behaviour, were studied in order to describe the transition from the 11 Å to the 9 Å phase by means of thermogravimetric-differential scanning calorimetry (TG-DSC) analyses as well as in situ and ex situ X-ray diffraction experiments. The TG-DSC analyses showed a continuous mass loss from 100 °C up to 700 °C, with different mass loss gradients between 100 °C up to 300 °C and between 300 °C up to 700 °C, corresponding to the dehydration of tobermorite and dehydroxylation of "tobermorite 9 A", respectively. Above 700 °C, "tobermorite 9 Å" is replaced by wollastonite. The X-ray powder diffraction data were collected at the GILDA beamline of the ESRF, Grenoble, France, from room temperature up to ca. 840 °C. Tobermorite is completely replaced by the 9 A phase at ca. 300 °C, whereas the latter is transformed into wollastonite at ca. 700 °C. The transition from the 11 Å to the 9 Å phase seems to be favoured by the transient appearance of a clinotobermorite-like compound