Clay minerals groups

Clay minerals are divided into three major groups. These are the important clay mineral groups. 

A superficial classification of the most common clay mineral groups can be based upon the number of ions present in the octahedral layer (2 diocatahedral or 3 trioctahedral) and the numbers and the kind of ions... 

Attention will be focused on two clay mineral groups kaolin and montmorillonite. Both groups have layered structures consisting of parallel sheets of oxide and hydroxide ions coordinated to Si4+ and Al3+ ions (233). Differences in the arrangement of the sheets and in their chemical composition give rise to the division into two groups. Within each group are several minerals of similar structure and composition. 

Name the various clay mineral groups present in soil. 

Know the general conditions of occurrence and stability of the major clay mineral groups, including the roles played by parent mineralogy, temperature, precipitation rate, soil drainage, and soil maturity in clay occurrence. 

Brown, G., 1961, Mineralogical Soc. of London, Clay Mineral Group, London, 544pp. 

Table 6.1. Stages of Soil Development as Indicated by the Presence of Clay Mineral Groups...

Table 10 Important applications for clay minerals grouped by clay type and application [8]...

Table 1.6 Average relative concentrations [wt.%] of the principal clay mineral groups in the < 2 Dm carbonate-free fraction in sediments from the major ocean basins (data from Windom 1976).

Table III summarizes the responses of the m ain clay mineral groups to various treatments and Figure 4 provides a generalized analytical procedure. These procedures outlined below are applicable for routine recognition and quantification of the major clay mineral groups. Within most of the groups there are various subgroups and species that require more elaborate XRD and chemical techniques not covered in this chapter. Brindley Brown (1980) and Thorez (1975) are excellent references that supply details about these more advanced techniques.

Table III. Response of major clay mineral groups to glycolation and healing (compiled from Brown Brindley, 1980 Thorez. 1975 and Carroll, 1970)... 

Calculation procedures Semi-quantitative calculations ofthe relative abundances of the major clay mineral groups are made using the weighted peak area method of Johns et al. (1954) ... 

The clay minerals are distinguished by their size (<2-3 pm) and extremely active surface chemistry. A few clay minerals, such as micas, do occur in silt and larger sizes. The most common clay mineral groups are those of kaolinite, smectite, and illite. Kaolinitic minerals are characterized by a rigidly held, hydrogen-bonded, nonexpansive, double-layer... 

Clay mineral group Cation exchange capacity (peq/gm of clay)... 

However, these reactions have to be seen as a strong simplification of the very complex clay mineral group and their formation processes. In the case of plagioclase, the weathering path is similar to that of K-feldspar and is accompanied by the release of sodium and/or calcium. Under low pH conditions plagioclase will react to form kaolinite, while under higher pH smectite will be formed. 

FIGURE 2 [010] view of structures of major clay mineral groups. 1 1 and 2 1 T 0... 

Chlorite group Clay minerals group Cobalt group Feldspar group Metal pigments Mica group Aluminium Aluminium hydroxide,... 

Aluminium group Chlorite group Clay minerals group Feldspar group Mica group Sheet silicates group Silicates group ... 

Clay minerals group Feldspar group Albite... 

Clay minerals group Maya blue Palygorskite... 

Aluminium group Clay minerals group Boehmite Diaspore Gibbsite Goethite HaUoysite Hematite Kaohnite Lepidocrocite Trolard Tardy (1987)... 

---