Silicate mineral

Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust.^[1][2][3]

In mineralogy, silica (silicon dioxide, SiO
2) is usually considered a silicate mineral rather than an oxide mineral. Silica is found in nature as the mineral quartz, and its polymorphs.

On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis.

Living organisms also contribute to this geologic cycle. For example, a type of plankton known as diatoms construct their exoskeletons ("frustules") from silica extracted from seawater. The frustules of dead diatoms are a major constituent of deep ocean sediment, and of diatomaceous earth.^{[citation needed]}

A silicate mineral is generally an inorganic compound consisting of subunits with the formula [SiO_2+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, M^x+. 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 ([SiO_2+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⁺.

In mineralogy, silicate minerals are classified into seven major groups according to the structure of their silicate anion:^[4][5]

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

• Phenakite group
  • Phenakite – Be
    2SiO
    4
  • Willemite – Zn
    2SiO
    4
• Olivine group
  • Forsterite – Mg
    2SiO
    4
  • Fayalite – Fe
    2SiO
    4
  • Tephroite – Mn
    2SiO
    4
• Garnet group
  • Pyrope – Mg
    3Al
    2(SiO
    4)
    3
  • Almandine – Fe
    3Al
    2(SiO
    4)
    3
  • Spessartine – Mn
    3Al
    2(SiO
    4)
    3
  • Grossular – Ca
    3Al
    2(SiO
    4)
    3
  • Andradite – Ca
    3Fe
    2(SiO
    4)
    3
  • Uvarovite – Ca
    3Cr
    2(SiO
    4)
    3
  • Hydrogrossular – Ca₃Al₂Si₂O₈(SiO₄)_3−m(OH)_4m
• Zircon group
  • Zircon – ZrSiO
    4
  • Thorite – (Th,U)SiO
    4
  • Hafnon – (Hf,Zr)SiO
    4

• Al
  2SiO
  5 group
  • Andalusite – Al
    2SiO
    5
  • Kyanite – Al
    2SiO
    5
  • Sillimanite – Al
    2SiO
    5
  • Dumortierite – Al_6.5–7BO₃(SiO₄)₃(O,OH)₃
  • Topaz – Al
    2SiO
    4(F,OH)
    2
  • Staurolite – Fe
    2Al
    9(SiO
    4)
    4(O,OH)
    2
• Humite group – (Mg,Fe)
  7(SiO
  4)
  3(F,OH)
  2
  • Norbergite – Mg
    3(SiO
    4)(F,OH)
    2
  • Chondrodite – Mg
    5(SiO
    4)
    2(F,OH)
    2
  • Humite – Mg
    7(SiO
    4)
    3(F,OH)
    2
  • Clinohumite – Mg
    9(SiO
    4)
    4(F,OH)
    2
• Datolite – CaBSiO
  4(OH)
• Titanite – CaTiSiO
  5
• Chloritoid – (Fe,Mg,Mn)
  2Al
  4Si
  2O
  10(OH)
  4
• Mullite (aka Porcelainite) – Al
  6Si
  2O
  13

Sorosilicates (from Greek σωρός Lua error: not enough memory. '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 – Lua error: not enough memory.
• Hemimorphite (calamine) – Lua error: Internal error: The interpreter exited with status 1.
• Lawsonite – Lua error: Internal error: The interpreter exited with status 1.
• Axinite – Lua error: Internal error: The interpreter exited with status 1.
• Ilvaite – Lua error: Internal error: The interpreter exited with status 1.
• Epidote group (has both Lua error: Internal error: The interpreter exited with status 1. and Lua error: Internal error: The interpreter exited with status 1. groups}
  • Epidote – Lua error: Internal error: The interpreter exited with status 1.
  • Zoisite – Lua error: Internal error: The interpreter exited with status 1.
    • Tanzanite – Lua error: Internal error: The interpreter exited with status 1.
  • Clinozoisite – Lua error: Internal error: The interpreter exited with status 1.
  • Allanite – Lua error: Internal error: The interpreter exited with status 1.
  • Dollaseite-(Ce) – Lua error: Internal error: The interpreter exited with status 1.
• Vesuvianite (idocrase) – Lua error: Internal error: The interpreter exited with status 1.

Cyclosilicates (from Greek Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 'circle'), or ring silicates, have three or more tetrahedra linked in a ring. The general formula is (Si_xO_3x)^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 (Si_2xO_5x)^2x− or a 2:5 ratio. The Nickel–Strunz classification is 09.C. Possible ring sizes include:

• 
  6 units Lua error: Internal error: The interpreter exited with status 1., beryl (red: Si, blue: O)
• 
  3 units Lua error: Internal error: The interpreter exited with status 1., benitoite
• 
  4 units Lua error: Internal error: The interpreter exited with status 1., papagoite
• 
  9 units Lua error: Internal error: The interpreter exited with status 1., eudialyte
• 
  12 units, double ring Lua error: Internal error: The interpreter exited with status 1., milarite

Some example minerals are:

• 3-member single ring
  • Benitoite – Lua error: Internal error: The interpreter exited with status 1.
• 4-member single ring
  • Papagoite – CaCuAlSi₂O₆(OH)₃.
• 6-member single ring
  • Beryl – Lua error: Internal error: The interpreter exited with status 1.
  • Bazzite – Lua error: Internal error: The interpreter exited with status 1.
  • Sugilite – Lua error: Internal error: The interpreter exited with status 1.
  • Tourmaline – (Na,Ca)(Al,Li,Mg)_3–(Al,Fe,Mn)₆(Si₆O₁₈)(BO₃)₃(OH)₄
  • Pezzottaite – Lua error: Internal error: The interpreter exited with status 1.
  • Osumilite – Lua error: Internal error: The interpreter exited with status 1.
  • Cordierite – Lua error: Internal error: The interpreter exited with status 1.
  • Sekaninaite – Lua error: Internal error: The interpreter exited with status 1.
• 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 – Lua error: Internal error: The interpreter exited with status 1.

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 Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. [genitive: Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1.] 'fibre'), or chain silicates, have interlocking chains of silicate tetrahedra with either Lua error: Internal error: The interpreter exited with status 1., 1:3 ratio, for single chains or Lua error: Internal error: The interpreter exited with status 1., 4:11 ratio, for double chains. The Nickel–Strunz classification is 09.D – examples include:

• Pyroxene group
  • Enstatite – orthoferrosilite series
    • Enstatite – Lua error: Internal error: The interpreter exited with status 1.
    • Ferrosilite – Lua error: Internal error: The interpreter exited with status 1.
  • Pigeonite – Lua error: Internal error: The interpreter exited with status 1.
  • Diopside – hedenbergite series
    • Diopside – Lua error: Internal error: The interpreter exited with status 1.
    • Hedenbergite – Lua error: Internal error: The interpreter exited with status 1.
    • Augite – Lua error: Internal error: The interpreter exited with status 1.
  • Sodium pyroxene series
    • Jadeite – Lua error: Internal error: The interpreter exited with status 1.
    • Aegirine (or acmite) – Lua error: Internal error: The interpreter exited with status 1.
  • Spodumene – Lua error: Internal error: The interpreter exited with status 1.
  • Pyroxferroite - Lua error: Internal error: The interpreter exited with status 1.
• Pyroxenoid group
  • Wollastonite – Lua error: Internal error: The interpreter exited with status 1.
  • Rhodonite – Lua error: Internal error: The interpreter exited with status 1.
  • Pectolite – Lua error: Internal error: The interpreter exited with status 1.

• Amphibole group
  • Anthophyllite – Lua error: Internal error: The interpreter exited with status 1.
  • Cummingtonite series
    • Cummingtonite – Lua error: Internal error: The interpreter exited with status 1.
    • Grunerite – Lua error: Internal error: The interpreter exited with status 1.
  • Tremolite series
    • Tremolite – Lua error: Internal error: The interpreter exited with status 1.
    • Actinolite – Lua error: Internal error: The interpreter exited with status 1.
  • Hornblende – (Ca,Na)_2–3(Mg,Fe,Al)₅Si₆(Al,Si)₂O₂₂(OH)₂
  • Sodium amphibole group
    • Glaucophane – Lua error: Internal error: The interpreter exited with status 1.
    • Riebeckite (asbestos) – Lua error: Internal error: The interpreter exited with status 1.
    • Arfvedsonite – Lua error: Internal error: The interpreter exited with status 1.

• 
  Inosilicate, pyroxene family, with 2-periodic single chain Lua error: Internal error: The interpreter exited with status 1., diopside
• 
  Inosilicate, clinoamphibole, with 2-periodic double chains Lua error: Internal error: The interpreter exited with status 1., 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 (from Greek Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 'leaf'), or sheet silicates, form parallel sheets of silicate tetrahedra with Lua error: Internal error: The interpreter exited with status 1. 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 subgroup
  • Antigorite – Lua error: Internal error: The interpreter exited with status 1.
  • Chrysotile – Lua error: Internal error: The interpreter exited with status 1.
  • Lizardite – Lua error: Internal error: The interpreter exited with status 1.
• Clay minerals group
  • 1:1 clay minerals (TO)
    • Halloysite – Lua error: Internal error: The interpreter exited with status 1.
    • Kaolinite – Lua error: Internal error: The interpreter exited with status 1.
  • 2:1 clay minerals (TOT)
    • Pyrophyllite – Lua error: Internal error: The interpreter exited with status 1.
    • Talc – Lua error: Internal error: The interpreter exited with status 1.
    • Illite – Lua error: Internal error: The interpreter exited with status 1.
    • Montmorillonite (smectite) – Lua error: Internal error: The interpreter exited with status 1.
    • Chlorite – Lua error: Internal error: The interpreter exited with status 1.
    • Vermiculite – Lua error: Internal error: The interpreter exited with status 1.
  • Other clay minerals
    • Sepiolite – Lua error: Internal error: The interpreter exited with status 1.
    • Palygorskite (or attapulgite) – Lua error: Internal error: The interpreter exited with status 1.
• Mica group
  • Biotite – Lua error: Internal error: The interpreter exited with status 1.
  • Fuchsite – Lua error: Internal error: The interpreter exited with status 1.
  • Muscovite – Lua error: Internal error: The interpreter exited with status 1.
  • Phlogopite – Lua error: Internal error: The interpreter exited with status 1.
  • Lepidolite – K(Li,Al)_2–3(AlSi₃)O₁₀(OH)₂
  • Margarite – Lua error: Internal error: The interpreter exited with status 1.
  • Glauconite – Lua error: Internal error: The interpreter exited with status 1.

• 
  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, or "framework silicates," have a three-dimensional framework of silicate tetrahedra with Lua error: Internal error: The interpreter exited with status 1. in a 1:2 ratio. This group comprises nearly 75% of the crust of the Earth.^[6] Tectosilicates, with the exception of the quartz group, are aluminosilicates. The Nickel–Strunz classifications are 09.F and 09.G, 04.DA (Quartz/ silica family). Examples include:

• 3D-Silicates, quartz family
  • Quartz – Lua error: Internal error: The interpreter exited with status 1.
  • Tridymite – Lua error: Internal error: The interpreter exited with status 1.
  • Cristobalite – Lua error: Internal error: The interpreter exited with status 1.
  • Coesite – Lua error: Internal error: The interpreter exited with status 1.
  • Stishovite – Lua error: Internal error: The interpreter exited with status 1.
  • Moganite – Lua error: Internal error: The interpreter exited with status 1.
  • Chalcedony – Lua error: Internal error: The interpreter exited with status 1.
• Tectosilicates, feldspar group
  • Alkali feldspars (potassium feldspars)
    • Microcline – Lua error: Internal error: The interpreter exited with status 1.
    • Orthoclase – Lua error: Internal error: The interpreter exited with status 1.
    • Anorthoclase – Lua error: Internal error: The interpreter exited with status 1.
    • Sanidine – Lua error: Internal error: The interpreter exited with status 1.
  • Plagioclase feldspars
    • Albite – Lua error: Internal error: The interpreter exited with status 1.
    • Oligoclase – Lua error: Internal error: The interpreter exited with status 1.     (Na:Ca 4:1)
    • Andesine – Lua error: Internal error: The interpreter exited with status 1.     (Na:Ca 3:2)
    • Labradorite – Lua error: Internal error: The interpreter exited with status 1.     (Na:Ca 2:3)
    • Bytownite – Lua error: Internal error: The interpreter exited with status 1.     (Na:Ca 1:4)
    • Anorthite – Lua error: Internal error: The interpreter exited with status 1.
• Tectosilicates, feldspathoid family
  • Nosean – Lua error: Internal error: The interpreter exited with status 1.
  • Cancrinite –Lua error: Internal error: The interpreter exited with status 1. • 2H₂O
  • Leucite – Lua error: Internal error: The interpreter exited with status 1.
  • Nepheline – Lua error: Internal error: The interpreter exited with status 1.
  • Sodalite – Lua error: Internal error: The interpreter exited with status 1.
  • Hauyne – (Na,Ca)_4–8Al₆Si₆(O,S)24(SO₄,Cl)_1–2
    • Lazurite – Lua error: Internal error: The interpreter exited with status 1.
• Tectosilicates, scapolite group
  • Marialite – Lua error: Internal error: The interpreter exited with status 1.
  • Meionite – Lua error: Internal error: The interpreter exited with status 1.
• Tectosilicates, zeolite family
  • Natrolite – Lua error: Internal error: The interpreter exited with status 1.
  • Erionite – Lua error: Internal error: The interpreter exited with status 1.
  • Chabazite – Lua error: Internal error: The interpreter exited with status 1.
  • Heulandite – Lua error: Internal error: The interpreter exited with status 1.
  • Stilbite – Lua error: Internal error: The interpreter exited with status 1.
  • Scolecite – Lua error: Internal error: The interpreter exited with status 1.
  • Mordenite – Lua error: Internal error: The interpreter exited with status 1.
  • Analcime – Lua error: Internal error: The interpreter exited with status 1.

• Earth:Classification of non-silicate minerals – Lua error: Internal error: The interpreter exited with status 1. – Lua error: Internal error: The interpreter exited with status 1.
• Earth:Classification of silicate minerals – Lua error: Internal error: The interpreter exited with status 1. – Lua error: Internal error: The interpreter exited with status 1.
• Chemistry:Silicate mineral paint – Lua error: Internal error: The interpreter exited with status 1. – Lua error: Internal error: The interpreter exited with status 1.

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

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pl:Krzemiany

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