X-Ray Diffraction Analysis

The X-ray diffraction (XRD) analyses are carried out to specify the mineralogical composition and determine semi-qualitatively the content of clay minerals in the tested samples. The most accepted clay samples from chemical analysis are examined and prepared for analyses as follows.

The samples are ground smaller than 75m and then are examined by XRD technique using (X'Pert Pro X-ray vertical diffractometer). The relationship between wavelength to the angle of diffraction and the original lattice or (d) spacing of the mineral under examination forms is known as Braggs Law (Dominic et al. 1993). The studied samples are analyzed using continuous scanning speed of 2/min. The X'Pert high score software release of the licensed

(1961) for estimating the clay minerals proportions in complex mixtures .

A-Kaolinite is characterized by a series of basal X- ray diffraction peaks at about 7.13 A° (001), 3.55 A (002) (Schultz, 1960 and grim, 1968). Glycolate yields no noteworthy shift in the spacing or intensity of the peaks. The heating specimen to 550°C lead to complete destruction of this pattern due to the collapse of the structure to an X-ray amorphous mineral (grim, 1968). b- Illite is characterized by a series of weak, broad X-ray diffraction peaks at 10 A° (001) and 3.3A° (003) that are not appreciably affected by either heat or glycolation treatment (grim, 1968). Illite is formed in soils with little chemical weathering and in areas of high relief where physical erosion is predominant (Chamley, 1989). c- Montmorillonite is characterized by cation exchange and the presence of water layer in its crystal lattice. It has a basal spacing of 12 A° for Na+ and 14A° for Ca+ montmorillonite (grim, 1968). Upon glycolation a characteristic swelling from d- spacing of 14A° to one of 18 A°, when heated at 550°C for two hours, the observed interlayer water causes a in the basal spacing decrease to about 10A° (Morkel,

The image is formed by a contrast between deferent features of the thin section (brightness, phase, color, polarization, fluorescence.) which depending on the lighting source to study the morphology and structure, shape of various features, including grains and phases instated by (Mukhopadhyay, 2003). The first step to prepare the thin section is cutting the specimen to a smaller size then polish by Rough Polishing powder decreasing to final polishing using abrasive sheet grinding silicon carbide coarse (600 μm) to fine (30 μm) at two sides of the surface of the samples then to expose the features of interest and protect the samples by covering with cove microscope glass using epoxy material, the etching by nital (1% nitric acid in isopropyl alcohol) dye make easier identification of some minerals, lite crystals reflect gray color but after etching reflect blue. Nital etch color is a function of a length of etching time, temperature, and reactivity of the crystal. Immerse the thin section in the solutions for 10-20 seconds, agitating gently to remove gas bubbles from the surface will show the effect of etching after Ono (1980).These steps are commonly referred to as metallography even though they apply to all