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General structure

A silicate mineral is generally an inorganic compound consisting of subunits with the formula [SiO2+n]2n−. Although depicted as such, the description of silicates as anions is a simplification. Balancing the charges of the silicate anions are metal cations, Mx+. Typical cations are Mg2+, Fe2+, and Na+. The Si-O-M linkage between the silicates and the metals are strong, polar-covalent bonds. Silicate anions ([SiO2+n]2n−) are invariably colorless, or when crushed to a fine powder, white. The colors of silicate minerals arise from the metal component, commonly iron.

In most silicate minerals, silicon is tetrahedral, being surrounded by four oxides. The coordination number of the oxides is variable except when it bridges two silicon centers, in which case the oxide has a coordination number of two.

Some silicon centers may be replaced by atoms of other elements, still bound to the four corner oxygen corners. If the substituted atom is not normally tetravalent, it usually contributes extra charge to the anion, which then requires extra cations. For example, in the mineral orthoclase [KAlSi3O8]n, the anion is a tridimensional network of tetrahedra in which all oxygen corners are shared. If all tetrahedra had silicon centers, the anion would be just neutral silica [SiO2]n. Replacement of one in every four silicon atoms by an aluminum atom results in the anion [AlSi3O−8]n, whose charge is neutralized by the potassium cations K+.

Main groups

In mineralogy, silicate minerals are classified into seven major groups according to the structure of their silicate anion:⁴⁵

Tectosilicates can only have additional cations if some of the silicon is replaced by an atom of lower valence such as aluminum. Al for Si substitution is common.

Nesosilicates or orthosilicates

Main category: Nesosilicates

Nesosilicates (from Greek νῆσος nēsos 'island'), or orthosilicates, have the orthosilicate ion, present as isolated (insular) [SiO4]4− tetrahedra connected only by interstitial cations. The Nickel–Strunz classification is 09.A –examples include:

• Phenakite group
  • Phenakite – Be2SiO4
  • Willemite – Zn2SiO4
• Olivine group
  • Forsterite – Mg2SiO4
  • Fayalite – Fe2SiO4
  • Tephroite – Mn2SiO4
• Garnet group
  • Pyrope – Mg3Al2(SiO4)3
  • Almandine – Fe3Al2(SiO4)3
  • Spessartine – Mn3Al2(SiO4)3
  • Grossular – Ca3Al2(SiO4)3
  • Andradite – Ca3Fe2(SiO4)3
  • Uvarovite – Ca3Cr2(SiO4)3
  • Hydrogrossular – Ca3Al2Si2O8(SiO4)3−m(OH)4m
• Zircon group
  • Zircon – ZrSiO4
  • Thorite – (Th,U)SiO4
  • Hafnon – (Hf,Zr)SiO4

• Al2SiO5 group
  • Andalusite – Al2SiO5
  • Kyanite – Al2SiO5
  • Sillimanite – Al2SiO5
  • Dumortierite – Al6.5–7BO3(SiO4)3(O,OH)3
  • Topaz – Al2SiO4(F,OH)2
  • Staurolite – Fe2Al9(SiO4)4(O,OH)2
• Humite group – (Mg,Fe)7(SiO4)3(F,OH)2
  • Norbergite – Mg3(SiO4)(F,OH)2
  • Chondrodite – Mg5(SiO4)2(F,OH)2
  • Humite – Mg7(SiO4)3(F,OH)2
  • Clinohumite – Mg9(SiO4)4(F,OH)2
• Datolite – CaBSiO4(OH)
• Titanite – CaTiSiO5
• Chloritoid – (Fe,Mg,Mn)2Al4Si2O10(OH)4
• Mullite (aka Porcelainite) – Al6Si2O13

Sorosilicates

Main category: Sorosilicates

Sorosilicates (from Greek σωρός sōros 'heap, mound') have isolated pyrosilicate anions Si2O6−7, consisting of double tetrahedra with a shared oxygen vertex—a silicon:oxygen ratio of 2:7. The Nickel–Strunz classification is 09.B. Examples include:

• Thortveitite – (Sc,Y)2(Si2O7)
• Hemimorphite (calamine) – Zn4(Si2O7)(OH)2·H2O
• Lawsonite – CaAl2(Si2O7)(OH)2·H2O
• Axinite – (Ca,Fe,Mn)3Al2(BO3)(Si4O12)(OH)
• Ilvaite – CaFeII2FeIIIO(Si2O7)(OH)
• Epidote group (has both (SiO4)4− and (Si2O7)6− groups}
  • Epidote – Ca2(Al,Fe)3O(SiO4)(Si2O7)(OH)
  • Zoisite – Ca2Al3O(SiO4)(Si2O7)(OH)
    • Tanzanite – Ca2Al3O(SiO4)(Si2O7)(OH)
  • Clinozoisite – Ca2Al3O(SiO4)(Si2O7)(OH)
  • Allanite – Ca(Ce,La,Y,Ca)Al2(FeII,FeIII)O(SiO4)(Si2O7)(OH)
  • Dollaseite-(Ce) – CaCeMg2AlSi3O11F(OH)
• Vesuvianite (idocrase) – Ca10(Mg,Fe)2Al4(SiO4)5(Si2O7)2(OH)4

Cyclosilicates

Main category: Cyclosilicates

Cyclosilicates (from Greek κύκλος kýklos 'circle'), or ring silicates, have three or more tetrahedra linked in a ring. The general formula is (SixO3x)2x−, where one or more silicon atoms can be replaced by other 4-coordinated atom(s). The silicon:oxygen ratio is 1:3. Double rings have the formula (Si2xO5x)2x− or a 2:5 ratio. The Nickel–Strunz classification is 09.C. Possible ring sizes include:

Some example minerals are:

• 3-member single ring
  • Benitoite – BaTi(Si3O9)
• 4-member single ring
  • Papagoite – CaCuAlSi2O6(OH)3.
• 6-member single ring
  • Beryl – Be3Al2(Si6O18)
  • Bazzite – Be3Sc2(Si6O18)
  • Sugilite – KNa2(Fe,Mn,Al)2Li3Si12O30
  • Tourmaline – (Na,Ca)(Al,Li,Mg)3–(Al,Fe,Mn)6(Si6O18)(BO3)3(OH)4
  • Pezzottaite – Cs(Be2Li)Al2Si6O18
  • Osumilite – (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30
  • Cordierite – (Mg,Fe)2Al4Si5O18
  • Sekaninaite – (Fe+2,Mg)2Al4Si5O18
• 9-member single ring
  • Eudialyte – Na15Ca6(Fe,Mn)3Zr3SiO(O,OH,H2O)3(Si3O9)2(Si9O27)2(OH,Cl)2
• 6-member double ring
  • Milarite – K2Ca4Al2Be4(Si24O60)H2O

The ring in axinite contains two B and four Si tetrahedra and is highly distorted compared to the other 6-member ring cyclosilicates.

Inosilicates

Main category: Inosilicates

Inosilicates (from Greek ἴς is [genitive: ἰνός inos] 'fibre'), or chain silicates, have interlocking chains of silicate tetrahedra with either SiO3, 1:3 ratio, for single chains or Si4O11, 4:11 ratio, for double chains. The Nickel–Strunz classification is 09.D – examples include:

Single chain inosilicates

• Pyroxene group
  • Enstatite – orthoferrosilite series
    • Enstatite – MgSiO3
    • Ferrosilite – FeSiO3
  • Pigeonite – Ca0.25(Mg,Fe)1.75Si2O6
  • Diopside – hedenbergite series
    • Diopside – CaMgSi2O6
    • Hedenbergite – CaFeSi2O6
    • Augite – (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
  • Sodium pyroxene series
    • Jadeite – NaAlSi2O6
    • Aegirine (or acmite) – NaFeIIISi2O6
  • Spodumene – LiAlSi2O6
  • Pyroxferroite - (Fe,Ca)SiO3
• Pyroxenoid group
  • Wollastonite – CaSiO3
  • Rhodonite – MnSiO3
  • Pectolite – NaCa2(Si3O8)(OH)

Double chain inosilicates

• Amphibole group
  • Anthophyllite – (Mg,Fe)7Si8O22(OH)2
  • Cummingtonite series
    • Cummingtonite – Fe2Mg5Si8O22(OH)2
    • Grunerite – Fe7Si8O22(OH)2
  • Tremolite series
    • Tremolite – Ca2Mg5Si8O22(OH)2
    • Actinolite – Ca2(Mg,Fe)5Si8O22(OH)2
  • Hornblende – (Ca,Na)2–3(Mg,Fe,Al)5Si6(Al,Si)2O22(OH)2
  • Sodium amphibole group
    • Glaucophane – Na2Mg3Al2Si8O22(OH)2
    • Riebeckite (asbestos) – Na2FeII3FeIII2Si8O22(OH)2
    • Arfvedsonite – Na3(Fe,Mg)4FeSi8O22(OH)2

Phyllosilicates

Main category: Phyllosilicates

Phyllosilicates (from Greek φύλλον phýllon 'leaf'), or sheet silicates, form parallel sheets of silicate tetrahedra with Si2O5 or a 2:5 ratio. The Nickel–Strunz classification is 09.E. All phyllosilicate minerals are hydrated, with either water or hydroxyl groups attached.

Examples include:

• Serpentine subgroup⁶
  • Amesite – Mg2Al(AlSiO5)(OH)4
  • Antigorite – Mg3Si2O5(OH)4
    • Bowenite – Mg3(Si2O5)(OH)4    (yellow variety of antigorite)⁷
  • Chrysotile – Mg3Si2O5(OH)4
  • Cronstedtite – Fe2+2Fe3+((Si,Fe3+)2O5)(OH)4
  • Lizardite – Mg3Si2O5(OH)4
  • Népouite – Ni3Si2O5(OH)4
  • Pecoraite – Ni3(Si2O5)(OH)4
• Clay minerals group
  • 1:1 clay minerals (TO)
    • Halloysite – Al2Si2O5(OH)4
    • Kaolinite – Al2Si2O5(OH)4
  • 2:1 clay minerals (TOT)
    • Pyrophyllite – Al2Si4O10(OH)2
    • Talc – Mg3Si4O10(OH)2
    • Illite – (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]
    • Montmorillonite (smectite) – (Na,Ca)0.33(Al,Mg)2Si4O10(OH)2·nH2O
    • Chlorite – (Mg,Fe)3(Si,Al)4O10(OH)2·(Mg,Fe)3(OH)6
    • Vermiculite – (Mg,Fe,Al)3(Al,Si)4O10(OH)2·4H2O
  • Other clay minerals
    • Sepiolite – Mg4Si6O15(OH)2·6H2O
    • Palygorskite (or attapulgite) – (Mg,Al)2Si4O10(OH)·4(H2O)
• Mica group⁸
  • Brittle mica group⁹
    • Anandite – (Ba,K)(Fe2+,Mg)3((Si,Al,Fe)4O10)(S,OH)2
    • Bityite – CaLiAl2(AlBeSi2O10)(OH)2
    • Clintonite – CaAlMg2(SiAl3O10)(OH)2
    • Margarite – CaAl2(Al2Si2)O10(OH)2
  • Dioctahedral mica group
    • Celadonite subgroup
      • Celadonite – K(MgFe3+◻)(Si4O10)(OH)2
      • Aluminoceladonite – K(MgAl◻)(Si4O10)(OH)2
    • Glauconite – K0.60−0.85(Fe3+,Mg,Al)2(Si,Al)4O10](OH)2
    • Muscovite – KAl2(AlSi3)O10(OH)2¹⁰
      • Fuchsite – K(Al,Cr)3Si3O10(OH)2    (Cr replaces Al in muscovite)¹¹
      • Illite – K0.6−0.85(Al,Mg)2(Si,Al)4O10(OH)2    (K-deficient muscovite)¹²
      • Mariposite – K(Al,Cr)2(Al,Si)4O10(OH)2    (Cr-bearing muscovite)¹³
      • Phengite – KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2    (Fe/Mg-bearing muscovite)¹⁴
    • Paragonite – NaAl2(AlSi3O10)(OH)2
    • Roscoelite – K(V3+,Al)2(AlSi3O10)(OH)2
  • Trioctahedral mica group
    • Aspidolite – NaMg3(AlSi3O10)(OH)2
    • Biotite subgroup – K(Fe2+,Mg)2(Al,Fe3+,Mg,Ti)([Si,Al,Fe]2Si2O10)(OH,F)2
      • Annite – KFe2+3(AlSi3O10)(OH)2
      • Phlogopite – KMg3(AlSi3)O10(OH)2
    • Hendricksite – KZn3(Si3Al)O10(OH)2
    • Lepidolite (polylithionite-trilithionite series) – K(Li2,Li1.5Al1.5)AlSi3−4O10(F,OH)2
    • Zinnwaldite series – KFe2+2Al(Al2Si2O10)(OH)2

Tectosilicates

Main category: Tectosilicates

Tectosilicates, or "framework silicates," have a three-dimensional framework of silicate tetrahedra with SiO2 in a 1:2 ratio. This group comprises nearly 75% of the crust of the Earth.¹⁵ Tectosilicates, with the exception of the quartz group, are aluminosilicates. The Nickel–Strunz classifications are 9.F (tectosilicates without zeolitic H2O), 9.G (tectosilicates with zeolitic H2O), and 4.DA (quartz/silica group). Below is a list of tectosilicate minerals and their chemical formulas, organized by groups and series:

• Quartz group (silica)
  • Quartz – SiO2
  • Tridymite – SiO2
  • Cristobalite – SiO2
  • Coesite – SiO2
  • Stishovite – SiO2
  • Moganite – SiO2
  • Chalcedony – SiO2
• Feldspar group¹⁶
  • Alkali feldspar series (potassium feldspars or K-spar)
    • Microcline – KAlSi3O8
      • Amazonite – green variety of microcline
    • Orthoclase – KAlSi3O8
      • Moonstone – opalescent variety of orthoclase
    • Anorthoclase – (Na,K)AlSi3O8
    • Sanidine – KAlSi3O8
  • Plagioclase feldspar series
    • Albite (sodium endmember) – NaAlSi3O8
    • Oligoclase – (Na,Ca)Al(Si,Al)Si2O8    (Na:Ca 90:10 to 70:30)¹⁷
    • Andesine – (Na,Ca)Al(Si,Al)Si2O8    (Na:Ca 50:50 to 70:30)¹⁸
    • Labradorite – (Ca,Na)Al(Al,Si)Si2O8    (Na:Ca 30:70 to 50:50)¹⁹
    • Bytownite – (Ca,Na)Al(Al,Si)Si2O8    (Na:Ca 10:90 to 30:70)²⁰
    • Anorthite (calcium endmember) – CaAl2Si2O8
  • Other feldspars
    • Buddingtonite — NH4AlSi3O8
    • Celsian – BaAl2Si2O8
    • Hyalophane – (K,Ba)[Al(Si,Al)Si2O8]²¹
    • Rubicline – (RbAlSi3O8²²
• Feldspathoid group²³
  • Cancrinite subgroup
    • Cancrinite – (Na,Ca,◻)8(Al6Si6O24)(CO3,SO4)2·2H2O
    • Afghanite – (Na,K)22Ca10[Si24Al24O96](SO4)6Cl6
    • Alloriite – (Na,Ca,K)26Ca4(Al6Si6O24)4(SO4)6Cl6
    • Bystrite – (Na,K)7Ca(Al6Si6O24)(S5)Cl
    • Farneseite – (Na,Ca,K)56(Al6Si6O24)7(SO4)12·6H2O
    • Sacrofanite – (Na61K19Ca32)(Si84Al84O336)(SO4)26Cl2F6·2H2O
    • Vishnevite – (Na,K)8(Al6Si6O24)(SO4,CO3)·2H2O
  • Danalite – Be3Fe²⁺4(SiO4)3S²⁴
  • Kalsilite – KAlSiO4
  • Leucite – K(AlSi2O6)
  • Nepheline subgroup
    • Nepheline – Na3K(Al4Si4O16)
    • Davidsmithite – (Ca,◻)2Na6Al8Si8O32
  • Sodalite subgroup
    • Sodalite – Na4(Si3Al3)O12Cl
    • Hauyne – Na3Ca(Si3Al3)O12(SO4)
    • Lazurite – Na7Ca(Al6Si6O24)(SO4)(S3)·H2O
    • Nosean – Na8(Al6Si6O24)(SO4)·H2O
    • Tugtupite – Na4(BeAlSi4O12)Cl²⁵
• Scapolite group²⁶
  • Marialite – Na4Al3Si9O24Cl
  • Meionite – Ca4Al6Si6O24CO3
• Zeolite group²⁷
  • Amicite – K2Na2Al4Si4O16·5(H2O)
  • Analcime – Na(AlSi2O6)·H2O
  • Brewsterite subgroup – (Ba,Sr,Ca)Al2Si6O16·5H2O
  • Chabazite-Lévyne subgroup
    • Chabazite – M[Al2Si4O12]·6H2O
    • Lévyne – (Ca1−2,Na1−2,K2)Al2Si4O12·6(H2O)
  • Clinoptilolite subgroup – (Na,Ca,K)3−6(Al6−7Si29−30O72)20H2O
  • Cowlesite – CaAl2Si3O10·6H2O
  • Dachiardite-K – K4(Si20Al4O48)·13H2O
  • Edingtonite – BaAl2Si3O10·4H2O
  • Erionite subgroup – (Na1−2,K1−2,Ca1−2)2Al4Si14O36·15H2O
  • Faujasite subgroup – (Na1−2,Ca1−2,Mg1−2)3.5[Al7Si17O48]·32(H2O)
  • Ferrierite subgroup – [Mg2(K,Na)2Ca0.5](Si29Al7)O72·18H2O    (Ferrierite-Mg)
  • Garronite-Ca – Na2Ca5Al12Si20O64·27H2O
  • Gismondine – CaAl2Si2O8·4(H2O)    (Gismondine-Ca)
  • Gmelinite subgroup – Na4(Si8Al4)O24·11H2O    (Gmelinite-Na)
  • Heulandite subgroup – (Na,Ca,K)5−6[Al8−9Si27−28O72]·nH2O
  • Hsianghualite – Ca3Li2(Be3Si3O12)F2
  • Laumontite – CaAl2Si4O12·4H2O
  • Mordenite – (Na2,Ca,K2)4(Al8Si40)O96·28H2O
  • Nabesite – Na2BeSi4O10·4H2O
  • Natrolite subgroup
    • Natrolite – Na2Al2Si3O10·2H2O
    • Gonnardite – (Na,Ca)2(Si,Al)5O10·3H2O
    • Mesolite – Na2Ca2Si9Al6O30·8H2O
    • Scolecite – CaAl2Si3O10·3H2O
  • Paulingite subgroup – (K2,Ca,Na2,Ba)5[Al10Si35O90]·45H2O    (Paulingite-K)
  • Phillipsite subgroup
    • Phillipsite – (Ca3(Si10Al6)O32·12H2O    (Phillipsite-Ca)
    • Harmotome – (Ba2(Si12Al4)O32·12H2O
  • Pollucite – (Cs,Na)2(Al2Si4O12)·2H2O
  • Stilbite subgroup
    • Stilbite – (NaCa4,Na9)(Si27Al9)O72·28H2O
    • Barrerite – Na2(Si7Al2)O18·6H2O
    • Stellerite – Ca4(Si28Al8)O72·28H2O
  • Thomsonite subgroup – NaCa2Al5Si5O20·6H2O    (Thomsonite-Ca)
  • Wairakite – Ca(Al2Si4O12)·2H2O
  • Yugawaralite – CaAl2Si6O16·4H2O

See also

• Earth sciences portal

• Classification of non-silicate minerals – List of IMA recognized minerals and groupings
• Classification of silicate minerals – List of IMA recognized minerals and groupings
• Silicate mineral paint – Paint coats with mineral binding agents

External links

• Mindat.org, Dana classification
• Webmineral : Dana's New Silicate Classification

References

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2. Deer, W.A.; Howie, R.A.; Zussman, J. (1992). An introduction to the rock-forming minerals (2nd ed.). London: Longman. ISBN 0-582-30094-0. 0-582-30094-0 ↩

3. Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20th ed.). Wiley. ISBN 0-47180580-7. 0-47180580-7 ↩

4. Deer, W.A.; Howie, R.A., & Zussman, J. (1992). An introduction to the rock forming minerals (2nd edition ed.). London: Longman ISBN 0-582-30094-0 /wiki/ISBN_(identifier) ↩

5. Hurlbut, Cornelius S.; Klein, Cornelis ||1985). Manual of Mineralogy, Wiley, (20th edition ed.). ISBN 0-471-80580-7 /wiki/ISBN_(identifier) ↩

6. "Kaolinite-Serpentine Group". mindat.org. Hudson Institute of Mineralogy. Retrieved 25 June 2025. https://www.mindat.org/min-11136.html ↩

7. "Bowenite". mindat.org. Hudson Institute of Mineralogy. Retrieved 25 June 2025. https://www.mindat.org/min-744.html ↩

8. "Mica Group". mindat.org. Hudson Institute of Mineralogy. Retrieved 24 February 2025. https://www.mindat.org/min-6728.html ↩

9. "Brittle Mica". mindat.org. Hudson Institute of Mineralogy. Retrieved 24 February 2025. https://www.mindat.org/min-43757.html ↩

10. "Muscovite". mindat.org. Hudson Institute of Mineralogy. Retrieved 24 February 2025. https://www.mindat.org/min-2815.html ↩

11. "Fuchsite". mindat.org. Hudson Institute of Mineralogy. Retrieved 24 February 2025. https://www.mindat.org/min-1617.html ↩

12. "Illite". mindat.org. Hudson Institute of Mineralogy. Retrieved 24 February 2025. https://www.mindat.org/min-2011.html ↩

13. "Mariposite". mindat.org. Hudson Institute of Mineralogy. Retrieved 24 February 2025. https://www.mindat.org/min-10003.html ↩

14. "Phengite". mindat.org. Hudson Institute of Mineralogy. Retrieved 16 March 2025. https://www.mindat.org/min-3189.html ↩

15. Deer, W.A.; Howie, R.A.; Wise, W.S.; Zussman, J. (2004). Rock-forming minerals. Volume 4B. Framework silicates: silica minerals. Feldspathoids and the zeolites (2nd ed.). London: Geological Society of London. p. 982 pp. ↩

16. "Feldspar Group". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-1624.html ↩

17. "Oligoclase". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-2976.html ↩

18. "Andesine". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-220.html ↩

19. "Labradorite". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-2308.html ↩

20. "Bytownite". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-815.html ↩

21. "Hyalophane". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-1960.html ↩

22. "Rubicline". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-7276.html ↩

23. "Feldspathoid". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-47865.html ↩

24. "Danalite". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-1341.html ↩

25. "Tugtupite". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-4044.html ↩

26. "Scapolite". mindat.org. Hudson Institute of Mineralogy. Retrieved 23 February 2025. https://www.mindat.org/min-8778.html ↩

27. "Zeolite Group". www.mindat.org. Retrieved 22 February 2025. https://www.mindat.org/min-4395.html ↩