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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 à . Only one of the two polytypes could be refined: it has B11b space group symmetry and cell parameters a 5 6.735(2) Å , b 5 7.425(2) Å , c 5 27.987(5) Å , c 5 123.25(1)1. The refinement converged to R 5 0.152 for 1291 reflections with F o 44s(F o ). 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 2 O 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 5 Si 6 O 16 (OH) 2 Á 7H 2 O. J ournal

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In this chapter, we illustrate and discuss two distinct groups of microporous phases: the cancrinite group and the C-S-H compounds of the tobermorite and gyrolite families. The compounds in the fi rst group present a three-dimensional purely tetrahedral framework with, apart from a single exception, Si:Al ratio equal to 1; in the mineralogical classifi cations they are included among feldspathoids and are generally “regarded …… distinct from zeolites, in part, at least, because of the presence of large volatile anions” (Coombs et al. 1998). The members of the second group are characterized by mixed frameworks built up by silicon (and aluminum) tetrahedra and calcium polyhedra. A common feature of both groups is the modular character of their frameworks, which are built up through various stacking ways of a single module (as in the minerals of the cancrinite-davyne family) and two or more modules as in the case of the C-S-H phases

Exceptionally preserved delicate baleen microstructures have been found in association\ud with the skeleton of a late Miocene balaenopteroid whale in a dolomite concretion of the\ud Pisco Formation, Peru. Microanalytical data (scanning electron microscopy, electron probe\ud microanalysis, X-ray diffraction) on fossil baleen are provided and the results are discussed\ud in terms of their taphonomic and paleoecological implications. Baleen fossilization modes\ud at this site include molding of plates and tubules, and phosphatization. A rapid formation of\ud the concretion was fundamental for fossilization. We suggest that the whale foundered in a\ud soft sediment chemically favorable to rapid dolomite precipitation, allowing the preservation\ud of delicate structures. Morphometric considerations on the baleen plates and bristles\ud coupled with the reconstructed calcification of the latter permit speculation on the trophic\ud preferences of this balaenopteroid whale: the densely spaced plates and the fine and calcified\ud bristles provide evidence for feeding on small-sized plankton, as does the modern sei whale

The name ‘tobermorites’ includes a number of calcium silicate hydrate (C-S-H) phases differing in their hydration state and sub-cell symmetry. Based on their basal spacing, closely related to the degree of hydration, 14, 11 and 9 Å compounds have been described. In this paper a new nomenclature scheme for these mineral species is reported. The tobermorite supergroup is defined. It is formed by the tobermorite group and the unclassified minerals plombièrite, clinotobermorite and riversideite. Plombièrite (‘14 Å tobermorite’) is redefined as a crystalline mineral having chemical composition Ca5Si6O16(OH)2·7H2O. Its type locality is Crestmore, Riverside County, California, USA. The tobermorite group consists of species having a basal spacing of ~11 Å and an orthorhombic sub-cell symmetry. Its general formula is Ca4+x(AlySi6–y)O15+2x–y·5H2O. Its endmember compositions correspond to tobermorite Ca5Si6O17·5H2O (x = 1 and y = 0) and the new species kenotobermorite, Ca4Si6O15(OH)2·5H2O (x = 0 and y = 0). The type locality of kenotobermorite is the N'Chwaning II mine, Kalahari Manganese Field, South Africa. Within the tobermorite group, tobermorite and kenotobermorite form a complete solid solution. Al-rich samples do not warrant a new name, because Al can only achieve a maximum content of 1/6 of the tetrahedral sites (y = 1). Clinotobermorite, Ca5Si6O17·5H2O, is a dimorph of tobermorite having a monoclinic sub-cell symmetry. Finally, the compound with a ~9 Å basal spacing is known as riversideite. Its natural occurrence is not demonstrated unequivocally and its status should be considered as “questionable”. The chemical composition of its synthetic counterpart, obtained through partial dehydration of tobermorite, is Ca5Si6O16(OH)2. All these mineral species present an order-disorder character and several polytypes are known. This report has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification