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In a system containing a mixture of minerals, the mineral with the lowest electrode potential tends to oxidize before minerals with higher potentials. Metal bearing materials can be classified according to the inherent mineral types.


Mineral types

  • Oxides
  • Sulfides
  • Other types

In contact with an aqueous solution some mineral types will generate acidity while others will generate alkalinity. This is important when evaluating the potential for leaching and ARD.

  • Acid-consuming minerals: carbonates, hydroxides, oxides, silicates
  • Acid-producing minerals: Total oxidation of pyrite to sulfate will generate acidity

If there are many different mineral types in a material it is said to be complex or polymetallic.

Mineral type affects leachability

Leaching objects can broadly be classified into oxide and sulfide minerals though other leaching objects exist. Sulfide ores are not as easily leached as oxide ores. Ores containing a lot of sulfide may be advantageously bioleached or biooxidized. Sometimes the variability in leachability between different minerals can be of use so that the valuable metal is leached but contaminators stay bound to the residue.

Complex ores

  • Complex ores may cause pre-treatment and recovery problems.
  • For complex ores the concentration step must be repeated many times to obtain a pure enough concentrate. Every concentration cycle means losses of valuable material. Therefore complex ores will lose more valuable material during concentration.
  • The existence of certain minerals in the complex ore may affect leaching

See also

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