Recent analytical studies of coal have elucidated the modes of occurrence of many trace elements. Scanning electron microscope (SEM) work has shown that many trace elements can be present as micrometer-size accessory minerals. For example, Zn and Cd occur in sphalerite? Cu in chalcopyrite; Zr and Hf in zircon? rare earth elements (REE), Y, and Th in monazite and xenotime. Fission-track results indicate that U can occur as micrometer-size grains of uraninite, in zircons, or in organic combination. Most minerals in coals have either a detrital or an authigenic origin. More detailed studies are necessary to elucidate further the relationships among the trace elements, minerals, and organic components in coal.