Black Iron Oxide - Fe3O4 - Synthetic - 5 Pounds Fe3O4, also known as magnetite or Iron (II,III) Oxide This comes from a synthetic source and is produced by Rockwood Particle size runs about 0.30 micron Used in thermite welding, fertilizers, pigments, ceramics, along with a lot of other uses We sell bulk for so many different uses, we don't include any specific use instructions