Graphite formed in contact metamorphism of coaly materials as a result of igneous intrusion is referred to as coal graphite. High-resolution transmission electron microscopy imaging has revealed four types of microstructure representing different degrees of graphitization. Progressive stages of graphitization are pregraphitization (aromatic layer coal), preliminary graphitization (microcolumn graphite), medium graphitization (corrugated graphite) and high graphitization (stiff graphite). Linear correlations occur between R(max) and aromatic layer thickness versus d(002) spacing, but both have inflection points at d(002) = 0.3375 nm.