Chemical elements
    Physical properties
    Chemical properties
      Aluminium subfluoride
      Aluminium trifluoride
      Aluminium trichloride
      Aluminium tribromide
      Aluminium iodide
      Aluminium chlorate
      Aluminium perchlorate
      Aluminium bromate
      Aluminium periodate
      Aluminium suboxide
      Aluminium sesqui-oxide
      Aluminium peroxide
      Aluminium hydroxides
      Tricalcium aluminate
      Sodilim aluminate
      Aluminium sesqui-sulphide
      Aluminium selenide
      Aluminium telluride
      Aluminium sulphite
      Aluminium sulphate
      Sodium alum
      Potassium alum
      Ammonium alum
      Hydroxylamine alum
      Silver alum
      Aluminium dithionate
      Aluminium selenite
      Aluminium selenate
      Aluminium chromate
      Aluminium molybdate
      Aluminium silicomolybdate
      Aluminium tungstate
      Aluminium silicotungstate
      Aluminium phosphotungstate
      Aluminium nitride
      Aluminium phosphide
      Aluminium arsenide
      Aluminium nitrate
      Aluminium Phosphates
      Basic aluminium arsenite
      Aluminium carbide
      Aluminium carbonate
      Aluminium thiocyanate
      Aluminium oxalate
      Aluminium alkyls
      Aluminium Hydrocarbon
      Aluminium acetylacetonate
      Aluminium silicide
      Aluminium silicates
      Aluminosilicic acids aluminosilicates
      Aluminium Borides
      Aluminium Boride
      Aluminium Boride
      Aluminium borocarbides
      Aluminium borate
      Aluminium sodium perborate
    PDB 1a6e-1zca
    PDB 2b8w-3i62
    PDB 3kql-5ukd


Tourmaline is a borosilicate of aluminium, alkali metals, iron, and magnesium, containing water of constitution and a little fluorine. It may be regarded as derived from H9Al3B2(OH)2Si4O19 by the replacement of the nine hydrogen atoms by metals. It is a trigonal mineral (ditrigonal pyramidal; a:c = 1:0.4474); hardness, 7; density, 3.1. Tourmaline is an important rock-forming mineral; it is interesting as an excellent example of a crystal exhibiting polar symmetry and pyro-electric properties, and as a valuable material for the production of plane-polarised light. The colour of tourmaline varies greatly with its chemical composition, from colourless to red, green, brown, and black. Excellent tourmaline crystals, suitable for use as gem-stones, are found in Ceylon and also in Brazil.

© Copyright 2008-2012 by