Silicate minerals

Silicate minerals
Copper silicate mineral chrysocolla
Category	Mineral

Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of rock-forming minerals and make up approximately 90 percent of the Earth's crust. They are classified based on the structure of their silicate groups, which contain different ratios of silicon and oxygen.

Nesosilicates or orthosilicates

Basic (ortho-)silicate anion structure

Nesosilicate specimens at the Museum of Geology in South Dakota

Nesosilicates (from Greek νῆσος nēsos, island), or orthosilicates, have the orthosilicate ion, which constitute isolated (insular) [SiO₄]⁴⁻ tetrahedra that are connected only by interstitial cations. Nickel–Strunz classification: 09.A

• 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

Kyanite crystals (unknown scale)

• Al₂SiO₅ group
  • Andalusite – Al₂SiO₅
  • Kyanite – Al₂SiO₅
  • Sillimanite – Al₂SiO₅
  • Dumortierite – Al_6.5–7BO₃(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

Sorosilicate exhibit at Museum of Geology in South Dakota

Sorosilicates (from Greek σωρός sōros, heap, mound) have isolated double tetrahedra groups with (Si₂O₇)⁶⁻ or a ratio of 2:7. Nickel–Strunz classification: 09.B

• Hemimorphite (calamine) – Zn₄(Si₂O₇)(OH)₂·H₂O
• Lawsonite – CaAl₂(Si₂O₇)(OH)₂·H₂O
• Ilvaite – CaFe^II₂Fe^IIIO(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)
  • Clinozoisite – Ca₂Al₃O(SiO₄)(Si₂O₇)(OH)
  • Tanzanite – Ca₂Al₃O(SiO₄)(Si₂O₇)(OH)
  • Allanite – Ca(Ce,La,Y,Ca)Al₂(Fe^II,Fe^III)O(SiO₄)(Si₂O₇)(OH)
  • Dollaseite-(Ce) – CaCeMg₂AlSi₃O₁₁F(OH)
• Vesuvianite (idocrase) – Ca₁₀(Mg,Fe)₂Al₄(SiO₄)₅(Si₂O₇)₂(OH)₄

Cyclosilicates

Cyclosilicate specimens at the Museum of Geology, South Dakota

Cyclosilicates (from Greek κύκλος kuklos, circle), or ring silicates, have linked tetrahedra with (T_xO_3x)^2x− or a ratio of 1:3. These exist as 3-member (T₃O₉)⁶⁻ and 6-member (T₆O₁₈)¹²⁻ rings, where T stands for a tetrahedrally coordinated cation. Nickel–Strunz classification: 09.C

• 3-member ring
  • Benitoite – BaTi(Si₃O₉)
• 6-member ring
  • Axinite – (Ca,Fe,Mn)₃Al₂(BO₃)(Si₄O₁₂)(OH)
  • Beryl/Emerald – Be₃Al₂(Si₆O₁₈)
  • Sugilite – KNa₂(Fe,Mn,Al)₂Li₃Si₁₂O₃₀
  • Cordierite – (Mg,Fe)₂Al₃(Si₅AlO₁₈)
  • Tourmaline – (Na,Ca)(Al,Li,Mg)₃₋(Al,Fe,Mn)₆(Si₆O₁₈(BO₃)₃(OH)₄

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

• 
  Cyclosilicate, [Si₆O₁₈] – 6-membered single rings, beryl (red: Si, blue: O)
• 
  Cyclosilicate, [Si₃O₉] – 3-membered single ring, benitoite
• 
  Cyclosilicate, [Si₄O₁₂] – 4-membered single ring, papagoite
• 
  Cyclosilicate, [Si₉O₂₇] – 9-membered ring, eudialyte
• 
  Cyclosilicate, [Si₆O₁₈] – 6-membered double ring, milarite

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. Nickel–Strunz classification: 09.D

Single chain inosilicates

• Pyroxene group
  • Enstatite – orthoferrosilite series
    • Enstatite – MgSiO₃
    • Ferrosilite – FeSiO₃
  • Pigeonite – Ca_0.25(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 (Acmite) – NaFe^IIISi₂O₆
  • Spodumene – LiAlSi₂O₆
• Pyroxenoid group
  • Wollastonite – CaSiO₃
  • Rhodonite – MnSiO₃
  • Pectolite – NaCa₂(Si₃O₈)(OH)

Double chain inosilicates

• Amphibole group
  • Anthophyllite – (Mg,Fe)₇Si₈O₂₂(OH)₂
  • Cumingtonite 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) – Na₂Fe^II₃Fe^III₂Si₈O₂₂(OH)₂
    • Arfvedsonite – Na₃(Fe,Mg)₄FeSi₈O₂₂(OH)₂

• 
  Inosilicate, pyroxene family, with 2-periodic single chain (Si₂O₆), diopside
• 
  Inosilicate, clinoamphibole, with 2-periodic double chains (Si₄O₁₁), tremolite
• 
  Inosilicate, unbranched 3-periodic single chain of wollastonite
• 
  Inosilicate with 5-periodic single chain, rhodonite
• 
  Inosilicate with cyclic branched 8-periodic chain, pellyite

Phyllosilicates

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

Kaolinite

• Serpentine subgroup
  • Antigorite – Mg₃Si₂O₅(OH)₄
  • Chrysotile – Mg₃Si₂O₅(OH)₄
  • Lizardite – Mg₃Si₂O₅(OH)₄
• Clay minerals group
  • Halloysite – Al₂Si₂O₅(OH)₄
  • Kaolinite – Al₂Si₂O₅(OH)₄
  • Illite – (K,H₃O)(Al,Mg,Fe)₂(Si,Al)₄O₁₀[(OH)₂,(H₂O)]
  • Montmorillonite – (Na,Ca)_0.33(Al,Mg)₂Si₄O₁₀(OH)₂·nH₂O
  • Vermiculite – (MgFe,Al)₃(Al,Si)₄O₁₀(OH)₂·4H₂O
  • Talc – Mg₃Si₄O₁₀(OH)₂
  • Sepiolite – Mg₄Si₆O₁₅(OH)₂·6H₂O
  • Palygorskite (or attapulgite) – (Mg,Al)₂Si₄O₁₀(OH)·4(H₂O)
  • Pyrophyllite – Al₂Si₄O₁₀(OH)₂
• Mica group
  • Biotite – K(Mg,Fe)₃(AlSi₃)O₁₀(OH)₂
  • Muscovite – KAl₂(AlSi₃)O₁₀(OH)₂
  • Phlogopite – KMg₃(AlSi₃)O₁₀(OH)₂
  • Lepidolite – K(Li,Al)_2–3(AlSi₃)O₁₀(OH)₂
  • Margarite – CaAl₂(Al₂Si₂)O₁₀(OH)₂
  • Glauconite – (K,Na)(Al,Mg,Fe)₂(Si,Al)₄O₁₀(OH)₂
• Chlorite group
  • Chlorite – (Mg,Fe)₃(Si,Al)₄O₁₀(OH)₂·(Mg,Fe)₃(OH)₆

• 
  Phyllosilicate, mica group, muscovite (red: Si, blue: O)
• 
  Phyllosilicate, single net of tetrahedra with 4-membered rings, apophyllite-(KF)-apophyllite-(KOH) series
• 
  Phyllosilicate, single tetrahedral nets of 6-membered rings, pyrosmalite-(Fe)-pyrosmalite-(Mn) series
• 
  Phyllosilicate, single tetrahedral nets of 6-membered rings, zeophyllite
• 
  Phyllosilicate, double nets with 4- and 6-membered rings, carletonite

Tectosilicates

Tectosilicates, or "framework silicates," have a three-dimensional framework of silicate tetrahedra with SiO₂ or a 1:2 ratio. This group comprises nearly 75% of the crust of the Earth. Tectosilicates, with the exception of the quartz group, are aluminosilicates. Nickel–Strunz classification: 09.F and 09.G, 04.DA (Quartz/ silica family)

Quartz

Lunar Ferroan Anorthosite no. 60025 (Plagioclase Feldspar). Collected by Apollo 16 from the Lunar Highlands near Descartes Crater.

• Quartz group
  • Quartz – SiO₂
  • Tridymite – SiO₂
  • Cristobalite – SiO₂
  • Coesite – SiO₂
  • Stishovite – SiO₂
• Feldspar family
  • Alkali feldspars (potassium feldspars)
    • Microcline – KAlSi₃O₈
    • Orthoclase – KAlSi₃O₈
    • Anorthoclase – (Na,K)AlSi₃O₈
    • Sanidine – KAlSi₃O₈
    • Albite – NaAlSi₃O₈
  • Plagioclase feldspars
    • Albite – NaAlSi₃O₈
    • Oligoclase – (Na,Ca)(Si,Al)₄O₈ (Na:Ca 4:1)
    • Andesine – (Na,Ca)(Si,Al)₄O₈ (Na:Ca 3:2)
    • Labradorite – (Ca,Na)(Si,Al)₄O₈ (Na:Ca 2:3)
    • Bytownite – (Ca,Na)(Si,Al)₄O₈ (Na:Ca 1:4)
    • Anorthite – CaAl₂Si₂O₈
• Feldspathoid family
  • Nosean – Na₈Al₆Si₆O₂₄(SO₄)
  • Cancrinite – Na₆Ca₂(CO₃,Al₆Si₆O₂₄).2H₂O
  • Leucite – KAlSi₂O₆
  • Nepheline – (Na,K)AlSiO₄
  • Sodalite – Na₈(AlSiO₄)₆Cl₂
    • Hauyne – (Na,Ca)_4–8Al₆Si₆(O,S)24(SO₄,Cl)_1–2
  • Lazurite – (Na,Ca)₈(AlSiO₄)₆(SO₄,S,Cl)₂
• Petalite – LiAlSi₄O₁₀
• Scapolite group
  • Marialite – Na₄(AlSi₃O₈)₃(Cl₂,CO₃,SO₄)
  • Meionite – Ca₄(Al₂Si₂O₈)₃(Cl₂CO₃,SO₄)
• Analcime – NaAlSi₂O₆·H₂O
• Zeolite family
  • Natrolite – Na₂Al₂Si₃O₁₀·2H₂O
  • Erionite – (Na₂,K₂,Ca)₂Al₄Si₁₄O₃₆·15H₂O
  • Chabazite – CaAl₂Si₄O₁₂·6H₂O
  • Heulandite – CaAl₂Si₇O₁₈·6H₂O
  • Stilbite – NaCa₂Al₅Si₁₃O₃₆·17H₂O
  • Scolecite – CaAl₂Si₃O₁₀·3H₂O
  • Mordenite – (Ca,Na₂,K₂)Al₂Si₁₀O₂₄·7H₂O

Gallery

• 
  Nesosilicate (SiO₄)
• 
  Sorosilicate (Si₂O₇), as in suolunite
  [Ca₂Si₂O₅(OH)₂·H₂O
• 
  Tectosilicate, aluminosilicate 3D network, zeolite family, synthetic zeolite ZSM-5
• 
  Silica family (SiO₂ 3D network), β-quartz

See also

• Classification of non-silicate minerals
• Classification of silicate minerals
• Silicate mineral paint

Further references

• 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.

• 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.

• Hurlbut, Cornelius S. (1966). Dana's Manual of Mineralogy (17th ed.). ISBN 0-471-03288-3.

• Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20th ed.). Wiley. ISBN 0-471-80580-7.

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

External links

Media related to Silicates at Wikimedia Commons