Serpentine mineral groups structure

The micas are characterized by extended silicate sheets rather than chains. Their structures resemble the serpentine mineral group in that they are dom-... 

FIGURE 2 [010] view of structures of major clay mineral groups. 1 1 and 2 1 T 0 layers are represented by the primary units in serpentine-kaolin and talc-pyrophyllite, respectively. The c-sin (5 distance is the basal (001) c-axis d-spacing. Layer eharge per formula unit = X. (Reproduced with the permission of the Mineralogical Society of Great Britain and Ireland from Ref. 13.)... 

The three minerals kaolinite, dickite, and nacrite differ not in the fundamental nature of their structural units, but in the ways in which these units are stacked one on top of another. The numerous forms of cronstedite investigated by Steadman and Nuttall [1963, 1964] and of chrysotile and other serpentine minerals investigated by Whittaker and Zussman in numerous publications also differ from one another only in the ways the structural units are stacked. Thus, the many minerals in this group can be considered as polymorphic variants of a few basic structures. 

The crystal structures of all the minerals in the serpentine group contain the same basic building blocks. The basic unit is composed of a silicate sheet of composition (Si205) ", in which three of the O atoms in each tetrahedron are shared with adjacent tetrahedra (Fig. 2.2A), and a nonsilicate sheet of... 

Asbestos, which is a term for a group of hydrous magnesium silicate minerals with a fibrous texture, is another silicate of technological significance. The structure of these minerals is characterized by long silicate chains. The most important variety is chrysotile Mg3Si205(0H)4, a fibrous form of serpentine. 

The serpentine group of minerals, which include chrysotile asbestos, are almost identical in composition. The chemical composition of unit cell is Mg6(OH)8Si40io. Chrysotiles have layered or sheeted crystal structure containing a silica sheet of (Si20s) in which silica tetrahedra point one way (Streib 1978). A layer of brucite, Mg(OH)2, joins the silica tetrahedra on one side of the sheet structure. Two out of every three —OH are replaced by oxygen atoms. X-ray and electron microscope studies indicate... 

Clay minerals, the micas, chlorite, serpentine, talc, between them can also find within the group of minerals phyllosilicates or layered silicates. They all have different morphology, structure, and texture (Bergaya et al. 2009). The some representative layer silicates used mainly in nanocomposites-based starch are listed in Table 2. It is important to note that the some phyllosilicates do not display a normal layered strucmre, for example, the sepiolite shows a fibrous structure meanwhile halloysite has spheroidal aggregates morphology (Duquesque et al. 2007 Bergaya et al. 2009). 

Serpentines - If a magnesia octahedral layer rather than an alumina l er is joined to one sheet of silica rings, two minerals of the serpentine group result. These differ markedly from each other and from the analogous aliuninum-based kaolinite. One is the mineral antigorite, whose sheet structure does not... 

---