Borax is a salt (ionic compound), a hydrated or anhydrous borate of sodium. It is a colorless crystalline solid, that dissolves in water to make a basic solution. The borax method is a technique of artisanal gold mining, which uses borax as a flux to purify gold concentrates. By using borax, no mercury flour is produced, hence gold recovery increases.

This method relies on borax’s ability to lower all the minerals’ melting points. Since the gold is usually the heaviest of these minerals, it allows for concentrating the gold on the bottom of the crucible. The process requires considerably less heat than conventional refining methods, which can be obtainable even in remote locations (using charcoal).


  • Used as a flux to purify gold concentrates.
  • Causes the other minerals to oxidize and breakdown.
  • Incorporated in refining flux formulations to dissolve metal oxides and used as a flux in gold assaying.
  • More safety compared to the Mercury usage.



Appearance : White Crystalline solid
Melting point : 743 °C
Boiling point : 1,575°C
Density : 2.4 g/cm3
Solubility in Water : Soluble