Chemical properties of rocks and minerals

Each individual mineral and rock has a distinct chemical composition which can be written as chemical formula. Except for native elements, minerals are salts composed of positively charged cations (e.g. K+, Na+, Ca++, Fe+++) and negatively charged anionic groups (e.g. CO3, PO4). The list below gives the main mineral groups and examples of each corresponding anionic group.

• Arsenites and vanadates     AsO4   and   VO4
  (Adamite, Erythrite, Mimetite, Olivenite, Carnotite, Vanadinite)
• Carbonates     CO3
  (Calcite, Cerussite, Dolomite, Siderite, Smithsonite)
• Halides   Cl   Cl2   F   F2
  (Atacamite, Carnallite, Cryolite, Fluorite, Halite)
• Native elements     Au   Ag
  (Gold, Silver, Copper, Iron)
• Nitrates and borates     NO3   and   BO3  B3O4
  (Nitratine, Chambersite, Inderite, Borax)
• Oxides and hydroxides     O   O2   and   OH   (OH)2
  (Baddeleyite, Corundum, Chrysoberyl, Rutile, Goethite, Manganite)
• Molybdates and tungstates     MoO4   and   WO4
  (Ferrimolybdite, Wulfenite, Wolframite)
• Phosphates     PO4
  (Anapaite, Apatite, Brazilianite, Chalcosiderite, Fluorapatite, Herderite, Lazulite)
• Silicates     SiO4   Si2O4
• Sulphides     S   S2
  (Chalcocite, Cinnabar, Galena, Jamesonite, Pyrite, Sphalerite, Stibnite)
• Sulphates and chromates     SO4   and   CrO4
  (Anhydrite, Barite, Celestite, Sulphohalite)

Silicates - are the largest group. About 86% of the earth's volume is silicate. A complex form of other materials often surrounds silicate because of its ability to polymerise. The silicate group has been subdivided into a number of smaller groups using their mineral structures as a basis. These include:

1. Tectosilicates - quartz, feldspars, zeolites
2. Phyllosilicates - micas, serpentines, clays, chlorites
3. Inosilicates - pyroxenes, pyroxinoids
4. Cyclosilicates - tourmalines, beryl
5. Sorosilicates - epidote, vesuvianite
6. Nesosilicates - garnets, olivine, alumino-silicates