They are generally extracted from minerals containing chromium. So, what are these minerals containing chromium? In this regard, relevant people said that there are three main types that are more common, namely:

1. Hard chromium spinel: The chemical composition is (Mg, Fe) (Cr, Al) 2O4, containing 32-50% of Cr2O3. The morphology, physical properties, genesis, occurrence and use of chromium-rich crystallite and hard chromium spinel are the same as those of chromite. The methods of industrial production of metallic chromium include aluminum reduction, silicon reduction, carbon reduction and electrolysis.

2. Chromium-rich spar: also known as ferrochromium spinel or aluminum chromite, chemical composition is Fe (Cr, Al) 2O4, containing 32% to 38% of Cr2O3.

3. Chromite: The chemical composition is (Mg, Fe) Cr2O4, which is between ferrous chromite (FeCr2O4, containing 32.09% FeO, 67.91% of Cr2O3) and magnesia chromite (MgCr2O4, containing 100% Mg). Between 20.96% and 79.04% Cr2O3), some people usually call both ferrous chromite and magnesia chromite. Chromite is an equiaxed crystal system, the crystals are small octahedrons, usually granular and dense masses, black in color, brown streaks, semi-metallic luster, hardness 5.5, density 4.2-4.8, with Weakly magnetic. Chromite is a mineral of magmatic origin. It is produced in ultrabasic rocks. When the ore-bearing rock* is damaged by weathering, the chromite is often transferred to the placer. Chromite is the main mineral raw material for chromium smelting, and inferior ores rich in iron can be used as good refractory materials.