Occurrence of Metals

Metals occur in nature in free as well as combined form.

Free State

Metals having low reactivity show little affinity for air, moisture, carbon dioxide or other non-metals present in nature. Such metals may remain in elemental or native (free) state in nature. Such metals are called noble metals as they show the least chemical reactivity. For example gold, silver, mercury and platinum occur in free state.

Combined State

Most of the metals are active and combine with air, moisture, carbon dioxide and non-metals like oxygen, sulphur, halogens, etc. to form their compounds, like oxides, sulphides, carbonates, halides and silicates. i.e., they occur in nature in a combined state.

A naturally occurring material in which a metal or its compound occurs is called a mineral. A mineral from which a metal can be extracted economically is called an ore.

An ore is that mineral in which a metal is present in appreciable quantities and from which the metal can be extracted economically.

Important Ores

Native Metals

Gold (Au), Silver (Ag)

Oxide ores

Iron (Haematite, Fe2O3); Aluminium (Bauxite, Al2O3.2H2O); Tin (Cassiterite, SnO2); Copper (Cuprite, Cu2O); Zinc (Zincite, ZnO); Titanium (Ilmenite, FeTiO3, Rutile, TiO2)

Sulphide ores

Zinc (Zinc blende, ZnS); Lead (Galena, PbS); Copper (Copper glance, Cu2S); Silver (Silver glance or Argentite, Ag2S); Iron (Iron pyrites, FeS2)

Carbonate ores

Iron (Siferite, FeCO3); Zinc (Calamine, ZnCO3); Lead (Cerrusite, PbCO3)

Sulphate ores

Lead (Anglesite, PbSO4)

Halide ores

Silver (Horn silver, AgCl); Sodium (Common salt or Rock salt, NaCl); Aluminium (Cryolite, Na3AlF6)

Silicate ores

Zinc (Hemimorphite, 2ZnO.SiO2.H2O)