This document describes methods for the determination of mineralogical phases often present as additives or reaction products in carbon containing or graphitic refractory products by X-ray Diffraction (XRD) using a Bragg-Brentano diffractometer. It includes details of sample preparation and general principles for qualitative and quantitative analysis of mineralogical phase composition. Quantitative determination of α-Si₃N₄, β-Si₃N₄, AlN, aluminium metal, Al₄C₃, silicon metal, boron carbide and BN are described. The problems encountered with some determinations are highlighted.

Additional reduced species present in some refractories could include Al₂O₃⋅AlN solid solutions (so called Alons), Si₃N₄⋅SiO₂ solid solutions and Si₃N₄⋅Al₂O₃ solid solutions (Sialons). The presence of some of these solid solution components will cause problems with both identification and quantification as they are not well-defined structures.