Mineral name. The chemical composition of Magnetite is Fe3O4, and the crystal belongs to Oxide mineral of equiaxed crystal system. The crystal is usually Octahedron and Rhombic dodecahedron, and the aggregate is granular or massive. The intact single crystal is Octahedron or Rhombic dodecahedron, and when it is Rhombic dodecahedron, the diamond plane often has stripes parallel to the long diagonal direction of the crystal plane. Aggregates are dense block or granular. The color is iron black, with black streaks, metallic or semi metallic luster, opaque, no cleavage, Mohs hardness of 5.5-6, and specific gravity of 4.8-5.3. Because it has strong magnetism, it is called a magnet in ancient Chinese books, indicating its magnetism; In addition, there are names such as iron ore, magnetite, and Xuanshi. The iron content is 72.4%, making it the most important iron ore. If the ore contains very few harmful elements, it can be directly used for open hearth steelmaking. Many Magnetite also contains titanium, vanadium, chromium and other elements, which can be comprehensively utilized during smelting. Magnetite is also one of the traditional Chinese medicinal materials. Traditional Chinese medicine believes that it has the effect of calming the nerves. The Magnetite crystal has an anti spinel structure (see spinel). Single crystals are usually Octahedron or Rhombic dodecahedron, and common aggregates of twins are massive or granular. Iron black, semi metallic luster, sometimes with Octahedron cleavage. Morse has a hardness of 5.5~6.5 and a specific gravity of 5.2. It has Ferrimagnetism. It is the most magnetic mineral and can be attracted by permanent magnets. Among them, polar Magnetite has extremely magnetic properties and can attract iron needles. Also known as Cishi, Magnetite, and Xuanshi. It is the most magnetic mineral that can be attracted by permanent magnets, and the ancient Chinese compass "Sinan" was made using this characteristic. It becomes Hematite or Limonite after oxidation. Magnetite crystals are usually Octahedron and Rhombic dodecahedron, and aggregates are granular or massive. It is the most magnetic mineral, which can be attracted by permanent magnets and become Hematite or Limonite after oxidation.