SILICATES

 

The silicates are the most abundant and chemically complex group of minerals.  All silicates have silica as the basis for their chemistry.  Silica is SiO2 chemistry.  The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid (the silica tetrahedron - SiO4).  Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon.  The resulting formula for silica is thus SiO2, not SiO4.

 

The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2).  All other silicates have silica + impurities.  Many silicates have a significant percentage of aluminum (the aluminosilicates).

 

 

  Quartz (SiO2)

 

  Opal (SiO2·nH2O)

 

  Potassium feldspar (KAlSi3O8 to (K,Na)AlSi3O8)

 

  Plagioclase feldspar (NaAlSi3O8 to CaAl2Si2O8)

 

  Nepheline ((Na,K)AlSiO4)

 

  Sodalite & Lazurite

 

  Analcime (NaAlSi2O6·H2O)

 

  Amphibole (hornblende, tremolite, actinolite, cummingtonite)

 

  Pyroxene (augite, diopside, bronzite, omphacite, jadeite)

 

  Spodumene (LiAlSi2O6)

 

  Olivine ((Mg,Fe)2SiO4)

 

  Garnet (almandine, grossular, spessartine, demantoid andradite,  melanite andradite)

 

  Mica (biotite, muscovite)

 

  Talc (Mg3Si4O10(OH)2)

 

  Tourmaline (schorl, dravite, elbaite, rubellite)

 

  Topaz (Al2SiO4(F,OH)2)

 

  Staurolite (Fe2Al9O6(SiO4)4(O,OH)2)

 

  Zircon (ZrSiO4)

 

  Kyanite (Al2SiO5)

 

  Beryl (Be3Al2(Si6O18)) (beryl, emerald, aquamarine, morganite, heliodor, goshenite)

 

  Serpentine (Mg3Si2O5(OH)4) (antigorite, chrysotile)

 

  Epidote

 

  Chlorite

 

  Kaolinite (Al2Si2O5(OH)4)

 

  Rhodonite (MnSiO3)

 

  Hemimorphite (Zn4(Si2O7)(OH)2·H2O)

 

  Prehnite (Ca2Al(AlSi3O10)(OH)2)

 

  Zeolites

    Scolecite (CaAl2Si3O10·3H2O)

    Natrolite (Na2Al2Si3O10·2H2O)

    Stilbite (NaCa2Al5Si13O36·14H2O)

 

  Chrysocolla ((Cu,Al)2H2Si2O5(OH)4·nH2O)

 

  Dioptase (Cu6(Si6O18)·6H2O)

 

  Tanzanite (vanadiferous zoisite) (Ca2Al3Si3O12(OH))

 

  Datolite (CaB(SiO4)(OH))

 

  Benitoite (BaTiSi3O9)

 

  Neptunite (Na2KLi(Fe,Mn)2Ti2Si8O24)

 

  Joaquinite (Ba2NaCe2FeTi2Si8O26(OH,F)·H2O)

 

  Cavansite (Ca(VO)Si4O10·4(H2O))

 

  Charoite ((K,Na)3(Ca,Sr,Ba,Mn)5Si12O30(OH·F)·3H2O)

 

  Palygorskite ((Mg,Al)2Si4O10(OH)·4H2O)

 

  Ilvaite (CaFe+3(Fe+2)2O(Si2O7)(OH))

 

  Okenite (CaSi2O5·2H2O)

 

  Sugilite (KNa2(Fe,Mn,Al)2Li3Si12O30)

 

  Danburite (CaB2(SiO4)2)

 

  Axinite Ca2(Mn,Fe,Mg)Al2BSi4O15(OH))

 

 

 

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