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Davidsmithite

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Formula:
(Ca,□)2Na6Al8Si8O32
Colour:
Colourless
Specific Gravity:
2.597 (Calculated)
Crystal System:
Hexagonal
Ca-analogue of nepheline, to which it is related by the heterovalent substitution of 2K+ by [Ca2+☐]. Davidsmithite completes the compositional space of the nepheline-structure group by providing a new root-composition, (Ca☐)2Na6Al8Si8O32.

Refered to as a "new K-poor, Ca-rich nepheline structure mineral" from the Liset eclogite, Sogn og Fjordane, Norway by Smith et al. (1986). Found in thin sections as a corona around anhedral crystals of lisetite. (Smith et al. 1986). At the type locality, it commonly overgrows lisetite.


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Classification of DavidsmithiteHide

Approved
Approval Year:
2016
First Published:
2017

Physical Properties of DavidsmithiteHide

Transparency:
Transparent
Colour:
Colourless
Cleavage:
None Observed
Density:
2.597 g/cm3 (Calculated)

Optical Data of DavidsmithiteHide

Type:
Uniaxial (-)
RI values:
nω = 1.538() nε = 1.535(2)
Max Birefringence:
δ = 0.003
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Low

Chemical Properties of DavidsmithiteHide

Formula:
(Ca,□)2Na6Al8Si8O32
IMA Formula:
(Ca,◻)2Na6Al8Si8O32

Crystallography of DavidsmithiteHide

Crystal System:
Hexagonal
Class (H-M):
6 - Pyramidal
Space Group:
P63
Cell Parameters:
a = 9.982(1) Å, c = 8.364(2) Å
Ratio:
a:c = 1 : 0.838
Unit Cell V:
721.74 ų
Z:
1

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
4.322(27)
4.182(66)
3.840(93)
3.267(71)
3.006(100)
2.882(41)
2.343(54)
2.305(31)

Type Occurrence of DavidsmithiteHide

Place of Conservation of Type Material:
Collections of the Muséum National d’Histoire Naturelle, Paris, France (thin section MNHN215-001)
Empirical Formula of Type Material:
([Ca0.6360.636]□0.414K0.165Na0.1492.000Na6.000(Al7.863Fe3+0.0197.882Si8.192O32
Geological Setting of Type Material:
In strongly retrograded layers in formerly jadeite-rich zones in a kyanite eclogite pod.
Associated Minerals at Type Locality:
Reference:
Kechid, S.-A., Parodi, G., Pont, S., Oberti, R. (2017) Davidsmithite, (Ca,□)2Na6Al8Si8O32: a new, Ca-bearing nepheline-group mineral from the Western Gneiss Region, Norway. European Journal of Mineralogy: 29: 1005-1013.

Synonyms of DavidsmithiteHide

Relationship of Davidsmithite to other SpeciesHide

Other Members of this group:
Cancrinite GroupA large, structurally complex group of alumosilicates.
CarnegieiteNaAlSiO4Tric.
KalsiliteKAlSiO4Hex. 6 2 2 : P63 2 2
LeuciteK(AlSi2O6)Tet. 4/m : I41/a
NephelineNa3K(Al4Si4O16)Hex. 6 : P63
Sodalite GroupThe Sodalite group have sodalite stacking producing cubo-octahedral cages that contain the anions and cations which ...
TrinephelineNaAlSiO4 Hex. 6 : P61

Other InformationHide

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 DavidsmithiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Smith, D.C., Kechid, S-A. and Rossi, G. (1986) Occurence and properties of lisetite, CaNa2Al4Si4O16, a new tectosilicate in the system Ca-Na-Al-Si-O. American Mineralogist: 71: 1372-1377. [as K-poor, Ca-rich nepheline structure mineral]
Kechid, S.-A., Oberti, R., Rossi, G., Parodi, G., Pont, P. (2016) Davidsmithite, IMA 2016-070. CNMNC Newsletter No. 34, December 2016, page 1317. Mineralogical Magazine: 80: 1315–1321.
Kechid, S.-A., Parodi, G., Pont, S., Oberti, R. (2017) Davidsmithite, (Ca,□)2Na6Al8Si8O32: a new, Ca-bearing nepheline-group mineral from the Western Gneiss Region, Norway. European Journal of Mineralogy: 29: 1005-1013. doi:10.1127/ejm/2017/0029-2667

Internet Links for DavidsmithiteHide

Localities for DavidsmithiteHide

This 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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Norway (TL)
 
  • Sogn og Fjordane
    • Selje
      • Liset
Kechid, S.-A., Oberti, R., Rossi, G., Parodi, G. and Pont, P. (2016) Davidsmithite, IMA 2016-070. CNMNC Newsletter No. 34, December 2016, page 1317; Mineralogical Magazine, 80, 1315–1321; Kechid, S.-A., Parodi, G., Pont, S., Oberti, R. (2017): Davidsmithite, (Ca,□)2Na6Al8Si8O32: a new, Ca-bearing nepheline-group mineral from the Western Gneiss Region, Norway. European Journal of Mineralogy, 29, 1005-1013
Mineral and/or Locality  
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