X-Ray Diffractometry (XRD) is the most important type of mineralogical analysis for identifying and studying crystalline substances. It makes use of the phenomenon of X-ray diffraction by crystalline lattice. Said technique is successfully utilised in numerous applications within the glass industry. This article describes the physical principles of XRD and the characteristics of a modern X-ray diffractometer which was recently purchased by the SSV. In the second part of the paper, practical examples are discussed, describing several important applications of XRD in the glass industry, including the analysis of raw materials, refractory materials, crystalline defects and the quantitative determination of crystalline silica exposure in work places.