4. Sources, deposits and reserves

Indium is a rare element, ranking 61st in terms of abundance in the Earth's crust, with an estimated mass concentration of 0.1 ppm.

Some zinc, lead, copper and iron sulfide minerals contain a few tenths of a percent indium. The strongly chalcophilic character of indium is similar to that of cadmium (Cd ²⁺ ), thallium (Tl ³⁺ ) and gallium (Ga ³⁺ ), and is superior to that of zinc (Zn ²⁺ ) and lead (Pb ²⁺ ). In addition, indium has a strong affinity for tin and copper.

It is commonly found in the crystal lattices of mineral species containing these two elements. In sphalerite (Zn, Fe)S, Zn is replaced by the (Cu, In) couple....