Solids can be crystalline or amorphous. Amorphous have a short-range order, while crystalline solids have a long-range order due to the fact that their structure can be described by periodic repetition of the unit cell. If crystals are exposed to X-rays, discrete diffracted X-rays are emitted, which enables us to identify substances in the samples with the help of computer programs. The rays are diffracted at angles, which are characteristic for each substance at the selected X-ray wavelength, so we can determine which substances are in the solid sample on the basis of the diffraction pattern, also called the diffractogram. In my diploma work, I used X-ray powder diffraction to determine which minerals make up the rocks and soil in the samples I collected in the vicinity of my home at Otočec in the Dolenjska region. For the characterization, I used the program Crystallographica Search Match - CSM, which reads a database of powder diffractograms of many standards (PDF) and compares them with the measured diffractogram of the sample.
I decided to sample at Otočec because I wanted to know more about the composition of the soil in the vicinity of my home. About 10 cm below the surface I collected 8 samples. I collected soil and stones at each location. Before measuring the diffraction patterns of the samples on the diffractometer, I ground and homogenized each sample in an agate mortar. By qualitative phase analysis with the CSM program I found that all rock samples were predominantly composed of dolomite. They also contained a small amount of quartz. In two of them I also identified a very small amount of calcite. The soil samples, however, contained a lot of quartz, except for one sample also a lot of dolomite. All soils contained a small amount of the silicate mineral microcline, and some of them also clinochlore and rutile. The composition of the soil is reasonable regarding to chemical weathering of such rocks.
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