INDEX interlayer cations

Figure 10-2 displays the powder XRD spectra of the five samples, as synthesized, and Table 10-3 shows, the X-ray powder diffraction data for the layer silicate phases. These spectra exhibit the charact stic bands (hk) at 4.45-4.47A, at nearly 2.56A, and at 1.49A. The 1.49A band (060) indicates the dioctahedral nature of the layer silicates. Due to the basal reflection, there is also a peak in the low-angle region, the value of which varied with interlayer cation nature and relative humidity (Table 10-4, third and fourth columns). Some samples show other peaks that may be indexed as (001) reflections such as (002), (004) or (006). 

Although the occurrence of clay vermiculites has been reported frequently in recent years. X-ray data on them are still rather limited, only data for the basal and 060 reflections being usually recorded. There is evidence that the nonbasal reflections can sometimes be indexed hkl, and it is probable that this is a general rule. As with the macroscopic minerals, the basal spacing varies with the nature of the interlayer cation and the hydration state of the specimen. If the 060 reflection lies in the range 1.49 to 1.51 A, the mineral is dioctahedral and, if in the range 1.53 to 1.55 A, trioctahedral (Stevens [1946], Walker [1950]). 

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