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Thaumasite

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Formula:
Ca3(SO4)[Si(OH)6](CO3) · 12H2O
System:
Hexagonal
Colour:
Colourless, white
Hardness:
Name:
From Greek, θαυµαζειν (thaumazein), to be surprised, alluding to its unusual composition with carbonate, sulphate and hexahydroxysilicate anions. First described by Nordenskiöld (1878)
Although it is generally assumed that a solid solution series between thaumasite and ettringite exists, both species have different space groups and a possible discontinuity was identified, characterised by a gap in the a-dimension of the solid solution phases (Barnett et al., 2000).

The Si analogue of Carraraite. Also compare Hielscherite and Chelyabinskite.

Visit gemdat.org for gemological information about Thaumasite.

Classification of Thaumasite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
7.DG.15

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
G : With large and medium-sized cations; with NO3, CO3, B(OH)4, SiO4 or IO3
32.4.4.4

32 : COMPOUND SULFATES
4 : Hydrated Compound Sulfates containing Hydroxyl or Halogen
17.10.18

17 : Silicates Containing other Anions
10 : Silicates with sulphate, molybdate or tungstate
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First Recorded Occurrence of Thaumasite

Year of Discovery:
1878

Physical Properties of Thaumasite

Vitreous
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Colourless, white
Streak:
White
Hardness (Mohs):
Cleavage:
Poor/Indistinct

Crystallography of Thaumasite

Crystal System:
Hexagonal
Class (H-M):
6 - Pyramidal
Space Group:
P63
Cell Parameters:
a = 11.030(7) Å, c = 10.396(6) Å
Ratio:
a:c = 1 : 0.943
Unit Cell Volume:
V 1,095.34 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Prismatic [0001], acicular.

Optical Data of Thaumasite

Type:
Uniaxial (-)
RI values:
nω = 1.507 nε = 1.468
Max Birefringence:
δ = 0.039
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate

Chemical Properties of Thaumasite

Formula:
Ca3(SO4)[Si(OH)6](CO3) · 12H2O
Essential elements:
All elements listed in formula:
Common Impurities:
Al,Fe,Mg

Relationship of Thaumasite to other Species

Other Members of Group:
BentoriteCa6(Cr3+,Al)2(SO4)3(OH)12 · 26H2O
BuryatiteCa3(Si,Fe,Al)(SO4)[B(OH)4]O(OH)5 · 12H2O
CarraraiteCa3(SO4)[Ge(OH)6](CO3) · 12H2O
CharlesiteCa6(Al,Si)2(SO4)2[B(OH)4](OH,O)12 · 26H2O
EttringiteCa6Al2(SO4)3(OH)12 · 26H2O
HielscheriteCa3Si(SO4)(SO3)(OH)6 · 11H2O
ImayoshiiteCa3Al(CO3)[B(OH)4](OH)6 · 12H2O
JouravskiteCa3Mn4+(SO4}(CO3)(OH)6 · 12H2O
KottenheimiteCa 3Si(SO4)2(OH)6·12H2O
Micheelsenite(Ca,Y)3Al(HPO4,CO3)(CO3)(OH)6 · 12H2O
SturmaniteCa6(Fe3+,Al,Mn3+)2(SO4)2[B(OH)4](OH)12 · 25H2O
7.DG.05DarapskiteNa3(SO4)(NO3) · H2O
7.DG.10Clinoungemachite(Na, K, Fe, SO4)
7.DG.10HumberstoniteNa7K3Mg2(SO4)6(NO3)2 · 6H2O
7.DG.10UngemachiteK3Na8Fe(SO4)6(NO3)2 · 6H2O
7.DG.15BentoriteCa6(Cr3+,Al)2(SO4)3(OH)12 · 26H2O
7.DG.15CharlesiteCa6(Al,Si)2(SO4)2[B(OH)4](OH,O)12 · 26H2O
7.DG.15EttringiteCa6Al2(SO4)3(OH)12 · 26H2O
7.DG.15JouravskiteCa3Mn4+(SO4}(CO3)(OH)6 · 12H2O
7.DG.15SturmaniteCa6(Fe3+,Al,Mn3+)2(SO4)2[B(OH)4](OH)12 · 25H2O
7.DG.15CarraraiteCa3(SO4)[Ge(OH)6](CO3) · 12H2O
7.DG.15BuryatiteCa3(Si,Fe,Al)(SO4)[B(OH)4]O(OH)5 · 12H2O
7.DG.20RapidcreekiteCa2(SO4)(CO3) · 4H2O
7.DG.20KorkinoiteCa4(SO4)2(CO3)2 · 9(H2O)
7.DG.25TatarskiteCa6Mg2(SO4)2(CO3)2(OH)4Cl4 · 7H2O
7.DG.30NakauriiteCu8(SO4)4(CO3)(OH)6 · 48H2O
7.DG.35Chessexite(Na,K)4Ca2(Mg,Zn)3Al8(SO4)10(SiO4)2 · 40H2O
7.DG.40CarlosruiziteK6(Na,K)4Na6Mg10(SeO4)12(IO3)12 · 12H2O
7.DG.40FuenzalidaiteK6(Na,K)4Na6Mg10(SO4)12(IO3)12 · 12H2O
7.DG.45Chelyabinskite(Ca,Mg)3(SO4,CO3)2[Si(OH)6] · 9H2O (?)
17.10.1NoseanNa8(Al6Si6O24)(SO4) · H2O
17.10.2PitiglianoiteNa6K2(Al6Si6O24)(SO4) · 2H2O
17.10.3Vishnevite(Na,K)8(Al6Si6O24)(SO4,CO3) · 2H2O
17.10.4Haüyne(Na,Ca)4-8(Al6Si6O24)(SO4,S,Cl)1-2
17.10.5Liottite(Na,K)16Ca8(Al6Si6O24)3(SO4)5Cl4
17.10.6Latiumite(Ca,K)4(Si,Al)5O11(SO4,CO3)
17.10.7Tuscanite(K(Ca,Na)6(Si,Al)10O22[SO4,CO3,(OH)2] · H2O
17.10.8MicrosommiteNa4K2Ca2(Al6Si6O24)(SO4)Cl2
17.10.9Delhayelite(Na,K)10Ca5Al6Si32O80(Cl2,F2,SO4)3 · 18H2O
17.10.10HydrodelhayeliteKCa2AlSi7O17(OH)2 · 6H2O
17.10.11Davyne(Na,K)6Ca2(Al6Si6O24)(Cl2,SO4)2
17.10.12Afghanite(Na,Ca,K)8(Al6Si6O24)(Cl2,SO4,CO3)3 · 0.5H2O
17.10.13Franzinite(Na,K)6Ca2(Al6Si6O24)(SO4)2 · 0.5H2O
17.10.14Giuseppettite(Na,K,Ca)7-8(Al6Si6O24)(SO4,Cl)1-2
17.10.15Sacrofanite(Na,K)98Ca20(Al6Si6O24)14(SO4)26Cl2 · 8H2O
17.10.16Chessexite(Na,K)4Ca2(Mg,Zn)3Al8(SO4)10(SiO4)2 · 40H2O
17.10.17InneliteNa2CaBa4Ti3(Si2O7)2(SO4)2O4
17.10.19Ellestadite
17.10.20Ellestadite-(Cl)Ca10(SiO4)3(SO4)3Cl2
17.10.21HydroxylellestaditeCa5(SiO4)1.5(SO4)1.5(OH)
17.10.22FluorellestaditeCa5(SiO4)1.5(SO4)1.5F
17.10.23MattheddleitePb5(SiO4)1.5(SO4)1.5(Cl,OH)
17.10.24QueititePb4Zn2(SO4)(SiO4)(Si2O7)
17.10.25RoeblingitePb2Ca6Mn2+(Si3O9)2(SO4)2(OH)2 · 4H2O
17.10.26YoshimuraiteBa2Mn2Ti(Si2O7)(PO4)O(OH)
17.10.27KegelitePb8Al4(Si8O20)(SO4)2(CO3)4(OH)8
17.10.28Wenkite(Ba,K)4(Ca,Na)6[(SO4)3|(Si,Al)20O39(OH)2] · 0.5H2O
17.10.29MacquartiteCu2Pb7(CrO4)4(SiO4)2(OH)2
17.10.30WeliniteMn62+(W6+,Mg)2(SiO4)2(O,OH)6

Other Names for Thaumasite

Name in Other Languages:

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.

References for Thaumasite

Reference List:
Nordenskiöld, A.E.(1878): Sur une nouvelle espèce minérale nommée thaumasite. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences. 87, 313-314.

Carpenter, A.B. (1963): Oriented overgrowths of thaumasite on ettringite. American Mineralogist. 48, 1394–1396.

Edge, R.A. and Taylor, H.F. (1971) Crystal structure of Thaumasite, [Ca3Si(OH)6·12H2O](SO4)(CO3). Acta Crystallographica. B27: 594-601.

Zemann, J. & Zobetz, E. (1981): Do the carbonate groups in thaumasite have anomalously large deviations from coplanarity? Kristallografija. 26, 1215–1217.

Effenberger, H., Kirfel, A., Will, G. & Zobetz, E. (1983): A further refinement of the crystal structure of thaumasite, Ca3Si(OH)6CO3SO4•12H2O. Neues Jahrbuch für Mineralogie. Monatshefte. 1983, 60-68.

Grubessi, O., Mottana, A., Paris, E. (1986): Thaumasite from the Tschwinning [N’Chwaning] mine, South Africa. Tschermaks Mineral. Petrogr. Mitt. 35, 149–156.

Barnett, S.J., Adam, C.D. & Jackson, A.R.W. (2000): Solid solutions between ettringite and thaumasite. Journal of Materials Science 35, 4109-4114.

Barnett, S.J., Adam, C.D. & Jackson, A.R.W. (2001): An XRPD profile fitting investigation of the solid solution between ettringite, Ca6Al2(SO4)3(OH)12.26H2O and carbonate ettringite, Ca6Al2(CO3)3(OH)12.26H2O. Cement and Concrete Research, 31, 13-17.

Jacobsen, S.D., Smyth, J.R., Swope, R.J. (2003) Thermal expansion of hydrated six-coordinate silicon in thaumasite, Ca3Si(OH)6 (CO3) (SO4) 12 H2O. Phys. Chem. Mineral. 30, 321–329.

Martucci, A. & Cruciani, G. (2006): In situ time resolved synchrotron powder diffraction study of thaumasite. Phys. Chem. Minerals 33, 723-731.

Internet Links for Thaumasite

Specimens:
The following Thaumasite specimens are currently listed for sale on minfind.com.

Localities for Thaumasite

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.
Mineral and/or Locality  
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