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Thomsonite-Ca

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Thomas Thomson
Formula:
NaCa2[Al5Si5O20] · 6H2O
System:
Orthorhombic
Colour:
Colourless, white, light ...
Hardness:
5 - 5½
Name:
Renamed in 1820 by Henry James Brooke in honor of Thomas Thomson [April 12, 1773 Crieff, Perthshire, Scotland - July 2, 1852 Kilmun, Argyleshire, Scotland], professor of chemistry at the University of Glasgow. Thomson was an indefatigable mineral chemist and contributed enormously to the number of accurate chemical analyses of minerals during his career as well as having discovered many new mineral species. The suffix -Ca denotes the dominance of calcium in the mineral.
Zeolite Group. Thomsonite Subgroup.
The calcium analogue of Thomsonite-Sr.


Classification of Thomsonite-Ca

Approved, 'Grandfathered' (first described prior to 1959)
9.GA.10

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H2O; zeolite family
A : Zeolites with T5O10 Units – The Fibrous Zeolites
16.10.4

16 : Silicates Containing Aluminum and other Metals
10 : Aluminosilicates of Ca and alkalis

Occurrences of Thomsonite-Ca

Type Occurrence of Thomsonite-Ca

Geological Setting of Type Material:
Amygdaloids in basalt.

Physical Properties of Thomsonite-Ca

Vitreous, Pearly
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Colourless, white, light yellow, light green, pink, brown
Streak:
White
Hardness (Mohs):
5 - 5½
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {010}
Good on {100}
Fracture:
Irregular/Uneven, Sub-Conchoidal
Density:
2.23 - 2.29 g/cm3 (Measured)    2.366 g/cm3 (Calculated)

Crystallography of Thomsonite-Ca

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 13.088(2) Å, b = 13.052(2) Å, c = 13.229(2) Å
Ratio:
a:b:c = 1.003 : 1 : 1.014
Unit Cell Volume:
V 2,259.84 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Crystals commonly prismatic, acicular, bladed, massive
Twinning:
On {110}. This twinning can be cyclic for repetition of 4 crystals.
Reference: Rudy Tschernich on Micro Probe (1996 vol. VIII, n. 4) SEM photo n.489 and one twinned crystal drawing. The sample is from Yellow Lake, Olalla, British Columbia, Canada
Comment:
Space group Pncn. Note: Thomsonite-Ca with disordered Al/Si-distribution has a = 13.0809(3), b = 13.0597(3), c = 6.6051(1) Å, V = 1128.37(14) Å3 and space group Pbnm (Gatta et al., 2010).
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Thomsonite-Ca

Type:
Biaxial (+)
RI values:
nα = 1.511 - 1.530 nβ = 1.513 - 1.532 nγ = 1.516 - 1.545
2V:
Measured: 44° to 75°, Calculated: 44° to 80°
Max Birefringence:
δ = 0.005 - 0.015
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r > v strong

Chemical Properties of Thomsonite-Ca

Formula:
NaCa2[Al5Si5O20] · 6H2O
All elements listed in formula:
Common Impurities:
K

Relationship of Thomsonite-Ca to other Species

Other Members of Group:
Thomsonite-SrNa(Sr,Ca)2[Al5Si5O20] · 7H2O
9.GA.05Gonnardite(Na,Ca)2(Si,Al)5O10 · 3H2O
9.GA.05MesoliteNa2Ca2Si9Al6O30 · 8H2O
9.GA.05NatroliteNa2Al2Si3O10 · 2H2O
9.GA.05ParanatroliteNa2Al2Si3O10 · 3H2O
9.GA.05ScoleciteCaAl2Si3O10 · 3H2O
9.GA.10Thomsonite-SrNa(Sr,Ca)2[Al5Si5O20] · 7H2O
9.GA.15EdingtoniteBa[Al2Si3O10] · 4H2O
9.GA.15KalborsiteK6Al4BSi6O20(OH)4Cl
16.10.1Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
16.10.2LisetiteCaNa2Al4Si4O16
16.10.5Gonnardite(Na,Ca)2(Si,Al)5O10 · 3H2O
16.10.6MesoliteNa2Ca2Si9Al6O30 · 8H2O
16.10.7Faujasite
16.10.8Garronite-CaNa2Ca5Al12Si20O64 · 27H2O
16.10.9BoggsiteCa8Na3(Si,Al)96O192 · 70H2O
16.10.10Herschelite(Na2,K2,Ca,Sr,Mg)2[Al2Si4O12]2 · 12H2O
16.10.11Phillipsite
16.10.12Fedorite(Na,K)2-3(Ca4Na3)Si16O38(OH,F)2 · 3.5H2O
16.10.13WillhendersoniteKCa[Al3Si3O12] · 5H2O
16.10.14Barrerite(Na,K,Ca0.5)2[Al2Si7O18] · 7H2O
16.10.15Mordenite(Na2,Ca,K2)Al2Si10O24 · 7H2O
16.10.16Reyerite(Na,K)2Ca14(Si,Al)24O58(OH)8 · 6H2O
16.10.17Lévyne
16.10.18Clinoptilolite
16.10.19Heulandite
16.10.20GobbinsiteNa5(Si11Al5)O32 · 11H2O
16.10.21Stilbite
16.10.22Dachiardite
16.10.23OffretiteKCaMg(Si13Al5)O36 · 15H2O
16.10.24PerlialiteK9Na(Ca,Sr)[Al2Si4O12]6 · 15H2O
16.10.25Erionite
16.10.26Paulingite
16.10.27Sodium Dachiardite(Na2,Ca,K2)4-5Al8Si40O96 · 26H2O
16.10.28Mazzite-Mg(Mg,K,Ca)5(Si26Al10)O72 · 28H2O
16.10.29RoggianiteCa2Be(OH)2Al2Si4O13 · 2.5H2O

Other Names for Thomsonite-Ca

Other Information

Electrical:
Pyroelectric
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 Thomsonite-Ca

Reference List:
Wise, W. S. & Tschernich, R. W. (1978): Habit, crystal forms and composition of thomsonite. Can. Mineral. 16, 487-493.

American Mineralogist (1992): 77: 685.

Acta Crystallographica: C46: 1370-1373.

Lee, Y., J.A. Hriljac, A. Studer & T. Vogt (2004), Anisotropic compression of edingtonite and thomsonite to 6 GPa at room temperature: Physics and Chemistry of Minerals: 31: 22-27.

Kol’tsova, T. N. (2005): Zeolites of the natrolite-thomsonite series. Inorganic Materials, 41, 750-756.

Gatta, G. D., Kahlenberg, V., Kaindl, R., Rotiroti, N., Cappelletti, P. and de’ Gennaro, M. (2010): Crystal structure and low-temperature behavior of “disordered” thomsonite. American Mineralogist 95, 495-502.

In thomsonite-Ca page of Mindat is reported a twinning on (110). This twinning can be cyclic for repetition of 4 crystals.
Reference: Rudy Tschernich on Micro Probe (1996 vol. VIII, n. 4) SEM photo n.489 and one twinned crystal drawing. The sample is from Yellow Lake, Olalla, British Columbia, Canada

Internet Links for Thomsonite-Ca

mindat.org URL:
http://www.mindat.org/min-3941.html
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Specimens:
The following Thomsonite-Ca specimens are currently listed for sale on minfind.com.

Localities for Thomsonite-Ca

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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