Theory:

Chemical method or Leaching:
  
This method is used when the ore is in a very pure form.
 
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Leaching
  • The ore is treated with a suitable reagent such that the ore is soluble in it, but the impurities are not.
  • The impurities are removed by filtration.
  • The solution of the ore, i.e., the filtrate, is treated with a suitable reagent that precipitates the ore.
Example:
Bauxite \(Al_2O_3.2H_2O\), (the ore of aluminium).
The extraction of metal from metal oxide can be categorized into three types:
  
More reactive metals
Medium reactive metals
Less reactive metals
\(Na\), \(K\), \(Ca\), \(Mg\), \(Al\)
\(Zn\), \(Fe\), \(Pb\), \(Cu\)
\(Ag\), \(Hg\)
Electrolytic reduction of
metal oxide into metal
Chemical reduction of metal
oxide into metal using coke
Thermal decomposition of
metal oxide into metal
  
Occurrence of ores in Tamil Nadu:
  
The following minerals can be found in the state of Tamil Nadu.
 
Lime stone:
  • Coimbatore, Cuddalore, Dindugul
Gypsum:
  • Tiruchi and Coimbatore Districts
Titanium minerals:
  • Kanyakumari, Tirunelveli and Tuticorin.
Chromite:
  • Coimbatore and Salem district.
Magnetite:
  • Dharmapuri, Erode, Salem, Thiruvannamalai.
Tungsten:
  • Madurai and Dindugal.