Chromium (Cr) is an element arranged in subgroup VI of the fourth period in the periodical table of elements. Its atomic number is 24 and the atomic weight 51.996.      

Up to date, more than 50 chromium-bearing minerals have been found in nature, belonging to oxides, chromates and silicates in addition to minor hydroxides, iodates, nitrides and sulfides. Belonging to oxides, picotite-group minerals are major Cr-bearing minerals, including mainly chromite, (Mg, Fe)Cr2O4, which is intermediate in composition between ferrochromite (FeCr2O4, containing 32.09% of FeO and 67.91% of Cr2O3) and magnesiochromite (MgCr2O4, containing 20.96% of MgO and 79.04% of Cr2O3); chrome-rich spinel, also called chromohercynite or alumochromite, Fe(Cr, Al)2O4, containing 32%~38% of Cr2O3; and chrompicotite, (Mg, Fe)(Cr, Al)2O4, containing 32%~50% of Cr2O3.     

Chromite was discovered for the first time in the Urals, Russia in 1799. Up to now chromite has been found in over 40 countries and regions in the world and the total reserves are up to 3.7 billion tons and the annual output is higher than 10 million tons.     

Chromite found its application first in the chemical industry. In the early 19th century, it was used for metallurgical and refractory purposes. Chromite products then have been widely used in civil and defense industries with the development of science and industry. Chromium is therefore considered as one of the important strategic materials.     

Before 1949, chromite was found only in Kaishantun, Jilin Province and it was all plundered by Japanese invaders. The industrial development after the founding of the People's Republic of China in 1949 promoted geological exploration and chromic ore was found for the first time in the Helan Mountains in Inner Mongolia. After that, large Cr deposits were discovered early or late in Xinjiang, Xizang(Tibet) and Gansu. By 1997, the cumulative explored reserves of chromite had been 11.557 million tons.