Minerals and Ores

What are Minerals?

Elements or compounds which occur naturally in earth's crust are called Minerals.

These minerals may or may not contain metals.

Examples : Salt , Clay Marble.

What are Ores?

Those minerals which contain a very high percentage of a particular metal from which metal can be profitably extracted is called ores.

Example : 

• Aluminium Metal is extracted from Bauxite Ore
• Iron Metal is extracted from Hematite Ore
• Sodium Metal is extracted from Rock Salt

Difference between Minerals and Ores :

How are Different Metals Found Inside Earth's crust?

The earth’s crust is the major source of Metals.

• Reactive metals do not occur in their free state . 
• Metals like Potassium, Sodium, Calcium, Magnesium and Aluminium are found in a combined state as a sulphide ore or oxide ore.
• Less reactive metals are present in their free state , these metals are silver, gold, copper.

It depends on the reactivity of metal .

Least Reactive Metals

• They are found in free state in earth's crust

Example -Gold,Silver, Copper.

Moderately Reactive Metals 

• They are found in crust mainly as oxides , sulphides and carbonates .
• We extract Zinc Metal from Zinc Sulphide (Zinc blende ore) and extract Iron Metal from Iron Oxide(Haematite) .

Example - Zinc, Iron, Lead.

Highly Reactive Metals

• They are never found in their free state .
• They are normally found as metal chloride or metal oxide
• We extract Sodium from Sodium Chloride .
• We extract Aluminium from Aluminium Oxide .
• Example -Sodium, Potassium, Aluminium.

How do we obtain metal from its ore?

As we’ve seen, the Ore of a metal is not pure metal that we can directly use. 

• The ore has impurities, and the metal must be obtained from its compounds.
• The process of removing impurities from ores is known as Concentration / Enrichment .
• After the ore has been concentrated, the metal can be extracted from the ore. The process is known as Extraction .

Concentration/Enrichment of Ore and Gangue

What is Concentration/Enrichment of Ore?

Concentration or Enrichment iis the process of removal of unwanted particles or gangue from the ore. 

It is done prior to extraction of the ore.

Methods of concentration depend upon the difference in physical properties of gangue and ore.

• Concentration is done by various methods like :

1. Hydraulic Washing - A rapid stream of running water is used to wash the ore. The lighter impurities are washed away while the ore remains.
   Example : It is used for washing ores of tin and lead , whose gangue is lighter than the ore.
   
2. Magnetic Separation - Magnets are used to separate gangue and ore . Either the gangue or the ore is supposed to be attracted by magnets.

Example : Iron is attracted by magnets, whereas its ore hematite is not.

What is Gangue?

The unwanted impurities like sand , rocky material , mica , limestone etc., present in an ore are called Gangue . 

Methods of removing gangue from ore depend on differences in the physical properties or chemical properties of ore and gangue.