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Silica is the trivial name for the chemical compound silicon dioxide, SiO2. The term silica comprises all polymorphs of silicon dioxide. In geoscience literature, the term silica also includes silicic acid, H4SiO4, which forms when silica polymorphs and silicate minerals are dissolved in water.

Two groups of silica polymorphs can be distinguished by their molecular structure:
1. Polymorphs that are made of SiO4 tetrahedra: α-quartz, β-quartz, moganite, α-tridymite, β-tridymite, α-cristobalite, β-cristobalite, keatite, coesite and silica glass (lechatelierite) are pure silica polymorphs. Opal-AG, opal-AN, opal-C, opal-CT, melanophlogite and chibaite are silica polymorphs that contain impurities. Structurally, all these polymorphs are network silicates.
2. High-pressure polymorphs in which each silicon atom is surrounded by six oxygen atoms: stishovite and seiferite. Since these polymorphs are not made of SiO4 tetrahedra, they are not structurally related to silicates.

Classification of Silica

Other Names for Silica

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Silica in petrology

An essential component of (items highlighted in red)
Common component of (items highlighted in red)
Accessory component of (items highlighted in red)

References for Silica

Reference List:
Sosman, R.B. (1927) The Properties of Silica. 856 pp., New York.

Rogers, Austin Flint (1928), Natural history of the silica minerals: American Mineralogist: 13: 73-92;

Cartz, L. (1964) An X-ray diffraction study of the structure of silica glass. Zeitschrift für Kristallographie: 120: 241-260.

Robinson, H.A. (1965) On the structure of vitreous SiO2. I. A new pentagonal dodecahedral model. Journal Phys. Chem. Solids: 26: 209-222.

Henninger, E.H., Buschert, R.C., and Heaton, L. (1967) Atomic structure and correlation in vitreous silica by x-ray and neutron diffraction. Journal Phys. Chem. Solids: 28: 423-432.

Hicks, J.F.G. (1967) Structure of silica glass. Scence: 155: 459-461.

Kushiro, I. (1969), The system forsterite-diopside-silica with and without water at high pressures: American Journal of Science: 267: 269-294.

Mozzi, R.L. and Warren, B.E (1969) The structure of vitreous silica. Journalm of Applied Crystallography: 2: 164-172.

Bell, R.J. and Dean, P. (1972) The structure of vitreous silica: validity of the random network theory. Phil. Magazine: 25: 1381-1398.

Konnert, J.H. and Karle, J. (1972) Tridymite-like structure in silica glass. Nature Phys. Sci.: 236: 92-94.

Narten, A.H. (1972) Diffraction pattern and structure of non-crystalline BeF2 and SiO2 at 25°C. Journal Chem. Phys.: 56: 1905-1909.

Konnert, J.H. and Karle, J. (1973a) Crystalline ordering in silica and germania glasses. Science: 179: 177-179.

Konnert, J.H., Ferguson, G.A., and Karle, J. (1974) Structure of silica glass: rebuttal. Science: 184: 93.

Da Silva, J.R.G.D., Pinatti, D.G., Anderson, C.E., and Rudee, M.L. (1975) A refinement of the structure of vitreous silica. Phil. Magazine: 31: 713-717.

Yip, K.L. and Fowler, W.B. (1975) Electronic structure of E1' centers in SiO2. Physics Review B: B11: 2327-2338.

Gaskell, P.H. and Tarrant, I.D. (1980) Refinement of a random network model for vitreous silicon dioxide. Phil. Magazine: B42: 265-286.

Herms, G. and Steil, H. (1980) The pentagonal dodecahedral model of vitreous silica and its compatibility with diffraction experiments. Krist. Tech.-Cryst. Res. Tech.: 15: 879-884.

Konnert, J.H., D'Antonio, P., and Karle, J. (1982) Comparison of radial distribution function for silica glass with those for various bonding topologies: use of correlation function. Journal of Non-Crystalline Solids 53: 135-141.

Richet, P., Bottinga, Y., Deniélou, L., Petitet, J.P., and Téqui, C. (1982) Thermodynamic properties of quartz, cristobalite, and amorphous SiO2: drop calorimetry measurements between 1000 and 1800 K and a review from 0 to 2000 K. Geochimica et Cosmochmica Acta: 46: 2639-2658.

Jani, M.G., Bossoli, R.B., and Halliburton, L.E. (1983) Further characterization of the E1' center in crystalline SiO2. Physics Review: B 27: 2285-2293.

Johnson, P.A.V., Wright, A.C., and Sinclair, R.N. (1983) Neutron scattering from vitreous silica. II. Twin-axis diffraction experiments. Journal of Non-Crystalline Solids: 58: 109-130.

Smith, J.V. and Blackwell, C.S. (1983) Nuclear magnetic resonance of silica polymorphs. Nature: 303: 223-225.

Dupree, E. and Pettifer, R.F. (1984) Determination of the Si-O-Si angle distribution in vitreous silica by magic angle spinning NMR. Nature: 308: 523-525.

Coombs, P.G., De Natale, J.F., Hood, P.J., McElfresh, D.K., Wortman, R.S., and Shackelford, J.F. (1985) The nature of the Si-O-Si bond angle distribution in vitreous silica. Phil. Magazine: B51: L39-L42.

Gupta, R.P. (1985) Electronic structure of crystalline and amorphous silicon dioxide. Physical Review: B32: 8278-8292.

Galeener, F.L. and Wright, A.C. (1986) The J.C. Phillips model for vitreous SiO2: a critical appraisal. Solid State Commun.: 57: 677-682.

Gerber, T. and Himmel, B. (1986) The structure of silica glass. Journal of Non-Crystalline Solids: 83: 324-334.

Goodman, C.H.L. (1986) The structure of silica glass and its surface. Phys. Chem. Glasses: 27: 27-31.

Kusabiraki, K. (1987) Infrared and Raman spectra of vitreous silica and sodium silicates containing titanium. Journal of Non-Crystalline Solids: 95-96: 411-418.

Galeener, F.L. (1988) Current models for amorphous SiO2. In: The Physics and Technology of Amorphous SiO* (R.A.B. Devine, ed.) Plenum Press, New York, NY.

Griscom, D.L. (1989) Self-trapped holes in amorphous silicon dioxide. Physics review: B 40: 4224-4228.

Gladden, L.F. (1990b) Medium-range order in v-SiO2. Journal of Non-Crystalline Solids: 119: 318-330.

Guttman, L. (1990) Ring structure of the crystalline and amorphous forms of silicon dioxide. Journal of Non-Crystalline Solids: 116: 154-147.

Marians, C.S. and Burdett, J.K. (1990) Geometric constraints: a refined model for the structure of silica glass. Journal of Non-Crystalline Solids: 124: 1-21.

Marians, C.S. and Hobbs, L.W. (1990) Local structure of silica glasses. Journal of Non-Crystalline Solids: 119: 269-282.

Young-nian, X. and Ching, W.Y. (1991) Electronic and optical properties of all polymorphic forms of silicon dioxide. Physical review: B44: 11048-11059.

Leko, V.K. (1993) The structure of vitreous silica. Glass Phys. Chem.: 19: 351-374.

Li, D., Bancroft, G.M., Kasrai, M., Fleet, M.E., Secco, R.A., Feng,X.H., Tan, K.H., and Yang, B.X. (1994): X-ray absorption spectroscopy of silicon dioxide (SiO2) polymorphs: the structural characterization of opal. American Mineralogist: 79: 622-632.

Wright, A.C. (1994) Neutron scatterng from vitreous silica. V. The structure of vitreous silica: what have we learned from 60 years of diffraction studies? Journal of Non-Crystalline Solids: 179: 84-115.

Di Pomponio, A., Continenza, Lozzi, A.A., Passacantando, L., Santucci, M., and Picozzi, P. (1995) Electronic properties of crystalline and amorphous SiO2 investigated via all-electron calculations and photoemission spectroscopy. Solid State Communications: 95: 313-317.

LeBail, A. (1995) Modelling the silica glass structure by the Rietveld method. Journal of Non-Crystalline Solids: 183: 39-42.

Gaskell, P.H. and Wallis, D.J. (1996) Medum-range order in silica, the canonical network glass. Phys. Rev. Lett.: 76: 66-69.

MAuri, F., Pasquarello, A., Pfrommr, BG., Yoon, Y.-G., and Louie, S.G. (2000) Si-O-Si bond-angle distribution in vitreous silica from first principles 29Si NMR analysis. Phys. Rev.: B62: R4786-R4789.

Nakamura, M., Arai, M., Otomo, T., Inamura, Y., and Bennington, S.M. (2001) Dispersive excitation in different forms of SiO2 Journal of Non-Crystalline Solids: 293-295: 377-382.

Nakamura, M., Arai, M., Inamura, Y., and Otomo, T. (2003) Dynamical properties of vitreous silica around the first sharp diffraction peak. Phys. Rev.: B67: 064204.

Clark, T.M., Grandinetti, P.J., Florian, P., and Stebbins, J.F. (2004) Correlated structural distributions in silica glass. Phys. Rev.: B70: 064202.

Tucker, M.G., Keen, D.A., Dove, M.T., and Trachenko, K. (2005) Refinement of the Si-O-Si angle distribution in vitreous silica. Journal Phys. Condens. Matter: 17: S67-S75.

Uchino, T., Harrop, J.D., Taraskin, S.N., and Elliott, S.R. (2005) Real and reciprocal space structural correlations contributing to the first sharp diffraction peak in silica glass. Phys. Rev.: B71: 014202.

Internet Links for Silica URL:
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Localities for Silica

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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