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Of about 3000 minerals species only a few dozens are economically valuable. Metals in particular have marked the evolution of our civilisation: 9000BP copper, 6000BP smelting, 5000BP alloys of tin, copper, lead, Bronze age 5000-2650BP, post 2650BP Iron age. Some metals (uranium, iron, aluminium, tin) combine with oxygene to form oxyde whereas other (zinc, lead, iron, copper, molybdenum) combines with sulfur to form sulfide. Native metals such as gold, silver, and platnum do not combine with other elements.

The average concentration of the Earth's crust is about a few ppm for most metals . To be minable metals must be first concentrated in natural ore deposits. Most geological processes tend to concentrate metals.

Magmatic segregation: Early (density driven), late (chemically driven).

Sedimentary segregation (chemically driving).