| 词条 | Thaumasite |
| 释义 |
| name = Thaumasite | category = Sulfate minerals | boxwidth = | boxbgcolor = | image = Thaumasite w-prehnite Hydrous basic calcium carbonate sulfate and silicate Fairfax Quarry near Contraville Fairfax County Virginia 1641.jpg | imagesize = | caption = Thaumasite (white) with prehnite (green) from Fairfax Quarry, Virginia | formula = Ca3Si(OH)6(CO3)(SO4)·12H2O CaSi(OH)6·CaCO3·CaSO4·12H2O CaSiO3·CaCO3·CaSO4·15H2O | molweight = 622.62 g/mol | strunz = 7.DG.15 | system = Hexagonal | class = Pyramidal (6) H-M symbol: (6) | symmetry = P63 | unit cell = a = 11.030(7), c = 10.396(6) [Å]; Z = 2 | color = Colorless, white, pale yellow | habit = Prismatic, fibrous, massive, radial | twinning = | cleavage = Indistinct | fracture = Subconchoidal | tenacity = Brittle | mohs = 3.5 | luster = Vitreous to silky | polish = | refractive = nω = 1.498–1.507 nε = 1.458–1.470 | opticalprop = Uniaxial (-) | birefringence = δ = 0.039 | dispersion = | pleochroism = | fluorescence= | absorption = | streak = White | gravity = 1.877 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = | references = [1][2][3] }} Thaumasite is a silicate mineral with chemical formula Ca3Si(OH)6(CO3)(SO4)·12H2O. It occurs as colorless to white prismatic hexagonal crystals, typically as acicular radiating groups. It also occurs as fibrous masses. Its Mohs hardness is 3.5 and it has a specific gravity of 1.88 to 1.90. Optically it is uniaxial negative with indices of refraction of nω = 1.507 and nε = 1.468. It occurs as a hydrothermal alteration mineral in sulfide ore deposits and geothermal alteration of basalt and tuff. It occurs with zeolites, apophyllite, analcime, calcite, gypsum and pyrite.[1] Thaumasite can also be formed along with other calcium silicate hydrates (CSH) during cement alteration, especially when sulfate attack develops. It was first described in 1878 in Sweden and named from the Greek, "thaumazein", to be surprised, in reference to its unusual composition with carbonate, sulfate and hydroxysilicate anions.[3] The silicate structure of thaumasite is unusual due to the presence of non-tetrahedral silicon in its crystal lattice.[4][5] Indeed, an atypic octahedral configuration is observed for Si present in thaumasite in the form of hexahydroxysilicate: [Si(OH)6]2−, a species exhibiting a geometry similar to that of the hexafluorosilicate [SiF6]2−. See alsoOther calcium silicate hydrate (C-S-H) minerals:
References1. ^1 Mineral Handbook 2. ^Webmineral data 3. ^1 Mindat.org 4. ^{{Cite journal| doi = 10.1021/jp071343n| pmid = 17608517| volume = 111| issue = 30| pages = 8740–8745| last = Duffy| first = J. A.|author2=D. E. Macphee | title = The coordination number of silicon in silicon−oxygen compounds: The special case of 6-fold coordination in thaumasite| journal = The Journal of Physical Chemistry B| year = 2007}} 5. ^{{Cite journal| doi = 10.1007/s00269-003-0328-0| volume = 30| issue = 6| pages = 321–329| last = Jacobsen| first = S. D.|author2=J. R. Smyth |author3=R. J. Swope | title = Thermal expansion of hydrated six-coordinate silicon in thaumasite, Ca3Si(OH)6(CO3)(SO4)·12H2O| journal = Physics and Chemistry of Minerals| date = 2003-07-01|bibcode = 2003PCM....30..321J }} Further reading{{Cite journal| doi = 10.1016/S0958-9465(03)00121-5 | issn = 0958-9465 | volume = 25 | issue = 8 | pages = 991–996 | last = Aguilera | first = J. |author2=S. Martínez-Ramírez |author3=I. Pajares-Colomo |author4=M. T. Blanco-Varela | title = Formation of thaumasite in carbonated mortars | journal = Cement and Concrete Composites | accessdate = 2010-08-03 | date = December 2003 | url = http://www.sciencedirect.com/science/article/B6TWF-4979J9S-C/2/f67125433f87c0db9e029b368c957ec1 }}{{Cite journal | doi = 10.1023/A:1004898623884 | volume = 35 | issue = 16 | pages = 4109–4114 | last = Barnett | first = S. J. |author2=C. D. Adam |author3=A. R. W. Jackson | title = Solid solutions between ettringite, Ca6Al2(SO4)3(OH)12·26H2O, and thaumasite, Ca3SiSO4CO3(OH)6·12H2O | journal = Journal of Materials Science | year = 2000 |bibcode = 2000JMatS..35.4109B }}{{Cite journal | doi = 10.1016/S0008-8846(01)00750-5 | issn = 0008-8846 | volume = 32 | issue = 5 | pages = 719–730 | last = Barnett | first = S. J. |author2=D. E. Macphee |author3=E. E. Lachowski |author4=N. J. Crammond | title = XRD, EDX and IR analysis of solid solutions between thaumasite and ettringite | journal = Cement and Concrete Research | accessdate = 2010-08-03 | date = May 2002 | url = http://www.sciencedirect.com/science/article/B6TWG-44XC8CF-8/2/cdd4c383057e2d08e0e3147c980dd41b }} External links
8 : Calcium minerals|Sulfate minerals|Carbonate minerals|Cement|Concrete|Hydrates|Hexagonal minerals|Luminescent minerals |
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