Alumina minerals

Gibbsite:

  • Chemical Name & Formula: Aluminium Hydroxide (or Tri-hydroxide), Al(OH)3
  • Technical or Common Name(s): Alumina Trihydrate (or simply ‘Hydrate’), usually written in oxide notation as Al2O3.3H2O
  • The most abundant economic source of alumina. It is also the intermediate product in the refining process.
  • Requires the lowest refining temperature, typically 150oC.

Boehmite

  • Chemical Name & Formula: Aluminium Hydroxy-oxide, AlOOH
  • Technical or Common Name(s): Alumina Monohydrate, usually written in oxide notation as Al2O3.H2O
  • Requires higher refining temperatures, typically 240-260oC

Diaspore

  • Chemical Formula: AlOOH, but usually written in oxide notation as Al2O3.H2O
  • Has the same composition as boehmite but a different crystal form. It does not occur in tropical bauxites but is of importance in Europe & China.
  • Requires the highest refining temperatures to process,typically +260oC.

Source: World Bauxite Resources, USGS, CMGroup