Fibrous zeolite

Staples, LW. and Card, J.A. (1959) The fibrous zeolite erionite its occurrence. 

Table 2.7 Composition and Structural Characteristics of Some Fibrous Zeolites... 

The prevalence of plaques appears to vary with the type of fiber exposure. Plaques have been deseribed in anthophyllite miners, their families, and others dwelling in Paakldla, Finland (Hillerdal, 1980). In the United States plaque formation is eommon with ehrysotile exposure (Selikoff and Lee, 1979). Erionite, the fibrous zeolite, is assumed to be the eause of plaques deseribed in the population of the Cappodocian villages in Turkey, where mesothelioma has also been described (Baris et al., 1979). 

Only fibrous zeolites (natrolite, mesolite, scolecite, edingtonite) are in this group. In their topological symmetry there are two T sites, one having a multiplicity 1/4 of the other (from now on indicated as Tl and T2 respectively). These tetrahedra are connected to construct a building block formed by five 4-membered rings (see Fig. la). In the case of order, Tl is occupied by Si (and will be called Sil from now on), whereas T2 splits into two symmetrically independent tetrahedra, one occupied by Si, the other by A1 (called Si2 and A1 respectively). 

Fig. 2. "Long-range order coefficients Sj, for fibrous zeolites with Si/Al=1.5.

Fibrous zeolites (natrolite, scolecite, thomsonite, edingtonite) Fibrous clay minerals (attapulgite sepiolite)... 

Baris YI. 1991. Fibrous zeolite (Erionite)-related diseases in Turkey. Am J Ind Med 19 374-378. 

Erzen C, Eryilmaz M, Kalyoncu F, et al. 1991. CT findings in malignant pleural mesothelioma related to nonoccupational exposure to asbestos and fibrous zeolite (erionite). J Comput Assist Tomogr 15 256-260. 

FIG. 23.21 Stereoscopic photographs showing the structures of (a) paracelsian, BafAljSijOs), (b) a fibrous zeolite, Na(AlSi206).H20, and (c) ultramarine, Na8(AUSi6024)S2, as systems of linked (Al, Si)0 tetrahedra. 

Zeolites - I, us Advances in Chemistry Series 101, 102 (A.C.S. Washington, 1971) 526 pp, 459 pp Molecular Sieves, Advances in Chemistry Series 121 (A.C.S., Washington. 1973) 634 pp D. W, Breck, Zeolite Molecular Steves (John Wiley, New York, 1974) 771 pp Natural Zeolites Occurrence, Properties. Use, L. B. Sand, F. A. Mumpton, Eds. (Pergamon. Oxford, 197 ) Studies on fibrous zeolites as possible environmental hazards A N. Rohl er al. Science 216, 51B (1982) Y. I Baris, Arch, Environ. Health 37, 177 (1982). 

Kirfel and Gibbs concentrated on the electron density distributions and bonded interactions for the fibrous zeolites natrolite, mesolite and scolecite and related materials via accurate single-crystal X-ray diffraction. BCP properties of calculated densities supplement their study and relief maps of V p are inspected. A study of the lumps and holes in the VSCC of microporous zeolites such as natrolite were promised. The authors anticipated to be able to delineate the sites of reactivity. 

Gottardi proposed a classification scheme that is similar to the SBU classification of Breck et al. (1974) (Table 6.2), except that it includes some historical context of how zeolites were discovered and named. This scheme uses a combination of zeolite group names that have specific SBUs and is widely used by geologists and consists of some complex structural units of tetrahedron, whether finite or infinite, which are (a) the chain of fibrous zeolites (b) the single-connected 4-ring chain (c) the double-connected 4-ring chain ... 

Fig. 19. The structures of some fibrous zeolites. The structure of one tetrahedron chain is shown in (d ), in which the large circles represent silicon or aluminium atoms, the small circles oxygen atoms, and the heights of the atoms are given m A The same chain is represented diagrammatically in (d), where the numbers show the heights of silicon and aluminium atoms as multiples of c/8 (the c axis is 6 6 A., so that 3c/8 = 2 5 A.. 5c/8 = 4 1 A.). The linked chains are shown in (a), (6), (c) as arranged in edingtonite, thomsonite and the natrolite group, respectively, and m each the imit cell is indicated by dotted lines.

There are many more minerals that could be discussed ranging from wollas-tonite, to attapulgite clays, or zeolites. Some mineral zeolites are fibrous asbestos types of crystals. Natrolite, Na2Al2Si30io-2H20, is called Fibrous Zeolite. Zeolites are used extensively in detergents, throughout the world, as a poor substitute for phosphates, but it is unlikely that synthetic zeolites will cause problems as an... 

Judging by the differences in iron-contents of crocidolite and chrysotile. Hardy and Aust (1995) proposed that the high iron content of the amphibole asbestos fiber, crocidolite, was the cause of its much greater carcinogenicity than the chrysotile fiber, which, indeed, contains forty times less iron than crocidolite or amosite. However, the fibrous zeolite erionite, also contains much less iron (about 18 times less iron than the amphiboles, and is also much less tightly bound cf. van Oss et al.(1999). As the mechanisms of pulmonary carcinogenesis of amphibole asbestos needles and of erionite needles are remarkably similar, the differences in the iron contents of amphibole and chrysotile asbestos species appear to be irrelevant. 

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