Occurrence and Extraction of Metals: Occurrence of Metals and Minerals (For CBSE, ICSE, IAS, NET, NRA 2022)

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Occurrence of Metals

  • Metals occur in nature in free as well as combined form.
  • Some Metals having 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” .
  • For example, gold, silver, mercury and platinum occur in free state.
  • Some 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, Sulphide, carbonates, halides and silicates.
  • They occur in nature in combined state.
  • The main active substances present in nature are oxygen and carbon dioxide in the atmosphere, Sulphur and silicon in the earth ′ s crust and chloride ions in the sea water.
  • Thus, Most metals are present in nature in combined form as oxides, Sulphide, carbonate, halides and silicates.

Minerals

A naturally occurring material in which a metal or its compound occurs is called a mineral.

Ore

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

Gangue or Matrix

The rocky or earthy impurities accompanying the ores are termed as gangue or matrix.

Some Important Ores

Some Important Ores

Extraction of Metals

  • The process of extracting the metals from their ores and refining them is called metallurgy.
  • The choice of the process depends upon the nature of the ore and the type of the metals.
  • The metal content in the ore vary depending upon the impurities present and chemical composition of ores.

Steps involved in the extraction of metals from their ores are:

  • Crushing and pulverization
  • Concentration or dressing of the ore
  • Calcination or roasting of the ore
  • Reduction of metal oxides to free metal
  • Purification and refining of metal

Crushing and Pulverization

  • The ore is generally obtained as big rock pieces.
  • The big lumps of the ore are crushed to smaller pieces by using jaw-crushers and grinders as shown in fig.
Jaw Crusher

The crushed pieces of the ore are then pulverized (powdered) in a stamp mill shown in Fig

The Stamp Mill

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