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 (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
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)2Norbergite – 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 (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
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 (from Greek κύκλος kuklos, circle), or ring silicates, have linked tetrahedra with (TxO3x)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
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.
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
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 (Acmite) – NaFeIIISi2O6
Spodumene – LiAlSi2O6
Pyroxenoid group
Wollastonite – CaSiO3
Rhodonite – MnSiO3
Pectolite – NaCa2(Si3O8)(OH)
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 (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.
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
Fuchsite - K(Al,Cr)2(AlSi3O10)(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
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 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
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)6Cl2Hauyne – (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
