(1) Ferrochrome, the chemical composition is (Mg, Fe) Cr2O4, which is between ferrous chromite (FeCr2O4, containing FeO 32.09%, Cr2O3 67.91%) and magnesite (MgCr2O4, containing Mg 20.96%, Cr2O3 79.04 %), some people usually refer to ferrous chromite and magnesite as chromite. Chromite is an equiaxed crystal system, and the crystals are fine octahedral, usually granular and dense blocky aggregates, black in color, brown in streaks, semi-metallic luster, hardness 5.5, density 4.2-4.8, weak magnetic. Chromite is a magmatic origin mineral, which is produced in ultra-basic rocks. When the ore-bearing rocks are damaged by weathering, chromite is often transferred to sand ores. Chromite is the most important mineral raw material for chromium smelting. Inferior ores rich in iron can be used as advanced refractory materials.
(2) Chromium-rich spar, also known as ferrochrome spinel or aluminochromite, with a chemical composition of Fe (Cr, Al) 2O4, containing 32% to 38% of Cr2O3.
(3) Hard chrome spinel, the chemical composition is (Mg, Fe) (Cr, Al) 2O4, containing 32% to 50% of Cr2O3. The chromium-rich spinel and hard chrome spinel have the same morphology, physical properties, genesis, occurrence and use as chromite. The methods of industrial production of metal chromium include aluminum reduction method, silicon reduction method, carbon reduction method and electrolysis method.
