This Data Release contains lanthanide (i.e., rare earth element, REE), yttrium (Y), and scandium (Sc) concentrations for oil shales and kerogens isolated from those presented in the associated journal article "Role of Organic Matter and Thermal Maturation in Rare Earth Element Partitioning in the Middle Devonian Sequence of the Appalachian Basin". This dataset provides REE content for a diverse range of organic-rich mudstones from around the world with samples from the Cambrian through Eocene Periods.