Chemical composition: FeO31.03, Fe2O368.96. Among them, the isomorphic substitution of Fe3 includes Al3, Ti4, Cr3, V3, etc; Substitutes for Fe2 include Mg2, Mn2, Zn2, Ni2, Co2, Cu2, Ge2, etc. When Ti4 replaces Fe3, it is accompanied by Fe2-Fe3, Mg2-Fe2, and V3-Fe3; Ti can also exist in the form of directional intergrowth of small inclusions of Ilmenite or ilmenite, which is exsolved from Solid solution. At>600 ℃, Magnetite FeFe2O4-Fe2TiO4 complete Solid solution is formed, and the mineral structure formula is Fe3 [Fe21-xFe31-2xTi4x] O4 (0 ≤ x ≤ 0.2); Fe31.2-xFe2x-0.2 [Fe21.2Fe30.8-xTi4x] O4 (0.2 ≤ x ≤ 0.8); Fe32-2xFe22x-1 [Fe22-xTi4x] O4 (0.8 ≤ x ≤ 1); The cations in square brackets are Octahedron coordination. FeFe2O4-FeTiO3 complete Solid solution is formed at>500 ℃; With the decrease of temperature, Solid solution exsolved. When Ti4 replaces Fe3, when TiO2 is 25%, it is called titanium containing Magnetite. When there is more vanadium and titanium, it is called vanadium titanium Magnetite. Those containing chromium are called chrome Magnetite. Titanium Magnetite and vanadium titanium Magnetite form Solid solution at high temperature, and exsolution occurs when the temperature drops. It can be seen from the optical film that Ilmenite generated in Magnetite grains is often split along the Octahedron of Magnetite, called titanium iron Magnetite. Fe2 in Magnetite can be replaced by Mg2, forming a complete isomorphic series of Magnetite magnesite.