Analcime structure

Zeolite P-C (Analcime Structure Type). Zeolite P-C was crystallized from sodium aluminosilicophosphate gels prepared by simultaneously... 

A crystalline phase of beryllosilicate with analcime structure was obtained under hydrothermal conditions from starting material of composition NasBe15Si50ls NaCl. An analcime-like phase was obtained as a nearly pure phase at 200°C. A small amount of sodium chloride coexisted with the above phase. The lattice constant was a = 13.35 it 0.01A. The refractive index was 1.519 it 0.002, higher than that of normal analcime. The broad endothermic peak, indicating the dehydration of zeolitic water, was observed in the temperature range from 150° to 500°C on a DTA curve. The specimen showed little change of structure on heating to 500°C. These results indicate that a beryllosilicate with the analcime structure was prepared by direct synthesis. 

Table I. X-Ray Data for the Beryllosilicate with Analcime Structure...

A beryllosilicate with the analcime structure can be prepared by direct synthesis. The lattice constant, refractive index, and DTA data are presented for the compound. These results indicate that beryllium may occupy the tetrahedral sites, replacing aluminum in the zeolite structure. 

McConnell D (1952) Viseite, a zeolite with the analcime structure and containing hnked Si04, PO4 and Hx04 groups. Am Mineral 37 609-617... 

In part because of the open crystal structure and resulting low density characteristic of zeolite minerals, analcime is the most voluminous reaction product in the simulations. 

Topology is cubic, with one independent T site. The structure of analcime has been determined and refined for a long time in the cubic space group [50], even if there is evidence of its non-cubic symmetry. 

The postulated local Si, A1 ordering in analcime resembles the observed Si, A1 distribution in the structure of laumontite (8, 9) which is also composed of four-membered Si-rings linked to each other through A1 tetra-hedra. Analcime pseudomorphs after laumontite have been recorded (10). All 4-rings in laumontite are near parallel, and twinning of the type just described is not possible. 

The displacements of the framework atoms in the H structure of analcime from the symmetrized positions are listed in Table III. They are considerably larger than the displacements of 0.02-0.07 A found in synthetic zeolite NaA (3) which are the smallest displacements recorded so far in a pseudosymmetric structure. The displacement vectors in analcime can be related to the apparent temperature parameters of the A structure. Figure 3 shows the experimentally determined vibration ellipsoids of optically isotropic analcime (7). The strongly anisotropic ellipsoids are in reasonably good accord with the displacement vectors obtained independently by DLS. 

Figure 3. Analcime. Apparent thermal-motion probability ellipsoids of the T and 0 atoms in the A structure and the displacements from the symmetrized position obtained by DLS. Ellipsoids are based on thermal parameters reported by Knowles, Rinaldi, and Smith (7) and are scaled to enclose 50% probability. The diagrams were generated with the aid of computer program ortep by C.K. Johnson...

Another type of analcime concentrations in sedimentary rocks are analcimolites. These are rocks composed almost entirely of granular, spherulitic analcime. Beds up to 1 to 2 m thick have been described in Jurassic formations of Georgia (9). Similar rocks have been found by Buryanova (10) among analcime tuffs and tuffaceous sandstones of early Carboniferous deposits of Tuva. Analcimolites are structurally similar to the rocks described by Vanderstappen and Verbeek (11) in Cretaceous and Jurassic rocks of the Congo. These authors assumed a sedimentary... 

Natural and artificial permutites, such as analcime Na[AlSi206]H20, belong also to the zeolites, in which base exchange occurs, for example Ca2+ for Na+ (water softening). The organic permutites, so important nowadays in ion exchange, have the open structure in common with these silicates. 

Analcime Family. Table 9 lists all known aluminosilicate minerals with the ANA structure, with their compositions and type localities. It does not include all compositional variations, only those that have been given different mineral names. 

The hyperbolic description implies that to a reasonable approximation, tetrahedral water, silicate, silicon and germanium frameworks are characterised by a preferred area per vertex group and a preferred Gaussian curvature. Thus, identical tessellations of isometric surfaces, with equal areas and curvatures at corresponding points on the surface, should offer alternative possibilities for stable frameworks. Indeed this is the case for the zeolite frameworks, faujasite and analcime, which are related to each other through the Bonnet transformation. Within an intrinsic two-dimensional description, these two frameworks are indistinguishable. We have seen in section 2.6 that the Bonnet transformation describes well a number of characteristics of the fee -> bcc martensitic phase transformation in metals and alloys. The success of this model suggests that the hyperbolic picture, intuitive and obvious for zeolites, is also valid for other atomic structures. 

Phillips BL, Kirkpatrick RJ (1994) Short-range Si-Al order in leucite and analcime Determination of the configurational entropy from Al and variable temperature Si NMR spectroscopy of leucite, its Rb-and Cs-exchanged derivatives, and analcime. Am Mineral 79 1025-1031 Phillips BL, Kirkpatrick RJ (1995) High-temperature Si MAS NMR spectroscopy anorthite (CaAl2Si208) and its P 1 -11 structural phase transition. Phys Chem Miner 22 268-276. 

Still another special problem in CEC and ESP determinations occurs for soils of high pH containing significant amounts of the slightly soluble zeolite minerals. Zeolites such as analcime and leucine contain replaceable monovalent cations in their crystal lattices. These structural cations are readily displaced by other monovalent cations, but not by divalent cations. If a monovalent cation is used as the index or... 

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