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Sanidine

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Formula:
KAlSi3O8
System:
Monoclinic
Colour:
Colourless, white, grey, ...
Lustre:
Vitreous
Hardness:
6
Member of:
Name:
From the Greek "sanis" for "little plate" and "idos" for "to see."
Feldspar Group.
Common in volcanic rocks.

See also the other potassium-dominant feldspars microcline and orthoclase.

Visit gemdat.org for gemological information about Sanidine.

Classification of Sanidine

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.FA.30

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
76.1.1.2

76 : TECTOSILICATES Al-Si Framework
1 : Al-Si Framework with Al-Si frameworks
16.3.7

16 : Silicates Containing Aluminum and other Metals
3 : Aluminosilicates of K
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Type Occurrence of Sanidine

Year of Discovery:
1808

Occurrences of Sanidine

Geological Setting:
Acidic volcanic rocks

Physical Properties of Sanidine

Vitreous
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Colourless, white, grey, yellowish white, or reddish white
Streak:
White
Hardness (Mohs):
6
Tenacity:
Brittle
Cleavage:
Perfect
{001} Perfect, {010} distinct
Parting:
{100}
Fracture:
Irregular/Uneven, Conchoidal
Density:
2.56 - 2.62 g/cm3 (Measured)    2.56 g/cm3 (Calculated)

Crystallography of Sanidine

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Cell Parameters:
a = 8.6Å, b = 13.03Å, c = 7.17Å
β = 116.03°
Ratio:
a:b:c = 0.66 : 1 : 0.55
Unit Cell Volume:
V 721.96 ų (Calculated from Unit Cell)
Morphology:
Tabular with square cross section
Twinning:
Carlsbad - common
Baveno, Manebach - rarer
Comment:
High sanidine forms a series with high albite

Optical Data of Sanidine

Type:
Biaxial (-)
RI values:
nα = 1.518 - 1.525 nβ = 1.523 - 1.530 nγ = 1.525 - 1.531
2V:
Measured: 60° , Calculated: 48° to 64°
Max Birefringence:
δ = 0.007
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r < v distinct

Chemical Properties of Sanidine

Formula:
KAlSi3O8
Essential elements:
All elements listed in formula:
Common Impurities:
Fe,Ca,Na,H2O

Relationship of Sanidine to other Species

Member of:
Other Members of Group:
AlbiteNaAlSi3O8
Amazonite
Andesine(Na,Ca)[Al(Si,Al)Si2O8]
AnorthiteCaAl2Si2O8
Anorthoclase(Na,K)AlSi3O8
BanalsiteBaNa2[Al2Si2O8]2
Buddingtonite(NH4)AlSi3O8
Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
CelsianBaAl2Si2O8
DmisteinbergiteCaAl2Si2O8
Hyalophane(K,Ba)[Al(Si,Al)Si2O8]
Labradorite(Ca,Na)[Al(Al,Si)Si2O8]
MicroclineKAlSi3O8
Oligoclase(Na,Ca)[Al(Si,Al)Si2O8]
OrthoclaseKAlSi3O8
ParacelsianBaAl2Si2O8
ReedmergneriteNa[BSi3O8]
Slawsonite(Sr,Ca)Al2Si2O8
StronalsiteSrNa2[Al2Si2O8]2
SvyatoslaviteCaAl2Si2O8
9.FA.05KaliophiliteKAlSiO4
9.FA.05KalsiliteKAlSiO4
9.FA.05Nepheline(Na,K)AlSiO4
9.FA.05Panunzite(K,Na)AlSiO4
9.FA.05Trikalsilite(K,Na)AlSiO4
9.FA.05Yoshiokaite(Ca,Na)[Al(Al,Si)O4]
9.FA.05MegakalsiliteKAlSiO4
9.FA.10MalinkoiteNaBSiO4
9.FA.15VirgiliteLiAlSi2O6
9.FA.25LisitsyniteKBSi2O6
9.FA.30AdulariaKAlSi3O8
9.FA.30Anorthoclase(Na,K)AlSi3O8
9.FA.30Buddingtonite(NH4)AlSi3O8
9.FA.30CelsianBaAl2Si2O8
9.FA.30Hyalophane(K,Ba)[Al(Si,Al)Si2O8]
9.FA.30MicroclineKAlSi3O8
9.FA.30OrthoclaseKAlSi3O8
9.FA.30Rubicline(Rb,K)AlSi3O8
9.FA.30MonalbiteNaAlSi3O8
9.FA.35AlbiteNaAlSi3O8
9.FA.35Andesine(Na,Ca)[Al(Si,Al)Si2O8]
9.FA.35AnorthiteCaAl2Si2O8
9.FA.35Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
9.FA.35Labradorite(Ca,Na)[Al(Al,Si)Si2O8]
9.FA.35Oligoclase(Na,Ca)[Al(Si,Al)Si2O8]
9.FA.35ReedmergneriteNa[BSi3O8]
9.FA.40ParacelsianBaAl2Si2O8
9.FA.45SvyatoslaviteCaAl2Si2O8
9.FA.45KumdykoliteNaAlSi3O8
9.FA.50Slawsonite(Sr,Ca)Al2Si2O8
9.FA.55LisetiteCaNa2Al4Si4O16
9.FA.60BanalsiteBaNa2[Al2Si2O8]2
9.FA.60StronalsiteSrNa2[Al2Si2O8]2
9.FA.65DanburiteCaB2Si2O8
9.FA.65MaleeviteBaB2Si2O8
9.FA.65PekoviteSrB2Si2O8
9.FA.70Lingunite(Na,Ca)AlSi3O8
9.FA.75KokchetaviteKAlSi3O8
16.3.1LithositeK6Al4Si8O25 · 2H2O
16.3.2KaliophiliteKAlSiO4
16.3.3KalsiliteKAlSiO4
16.3.4LeuciteK(AlSi2O6)
16.3.5MicroclineKAlSi3O8
16.3.6OrthoclaseKAlSi3O8
16.3.8MuscoviteKAl2(AlSi3O10)(OH)2

Other Names for Sanidine

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 Sanidine

Reference List:
Klaproth, M.H. (1810): Chemische Untersuchung des glasigen Feldspaths vom Drachenfels, Beiträge zur chemischen Kenntniss der Mineralkörper, Fünfter Band, Rottmann Berlin, 12-18

Onorato E., Penta M., Sgarlata F. -(1963) Struttura del sanidino. Periodico di Mineralogia – Roma pp. 1-34.

Scott, R.B., Bachinski, S.W., Nesbitt, R.W., and Scott, M.R. (1971) Rate of Al-Si ordering in sanidines from an ignimbrite cooling unit. American Mineralogist: 56: 1208-1221.

Bertelmann, D., Förtsch, E., and Wondratscher, H. (1985) Zum Temperverhalten von Sanidin: die Ausnahmerolle der Eifelsanidin-Megakristalle. Neues Jahrbuch für Mineralogie, Abhandlungen: 152: 123-141.

Gering, E. (1985) Silizium/Aluminium-Ordnung und Kristallperfektion von Sanidinen. Dissertation, University of karlsruhe, Karlsruhe, Germany.

Bertelmann, D., Walther, J., and Wondratscher, H. (1987) Annealing-induced inclusions and transformation behaviour of Eifel sanidines. Terra Cognita: 7: 257-258.

Bernotat-Wulf, H., Bertelmann, D., and Wondratscher, H. (1988) The annealing behavour of Eifel sanidine (Volkesfeld). III. The influence of the sample surface and sample size on the order-disorder transformation rate. Neues Jahrbuch für Mineralogie, Monatshefte 1988: 504-515.

Ferguson, R.B., Ball, N.A., and Cerny, P. (1991) Structure refinement of an adularian end-member high sanidine from the Buck Claim pegmatite, Bernic Lake, Manitoba. Canadian Mineralogist: 29: 543-552.

Kroll, H. and Knitter, R. (1991) Al, Si exchange kinetics in sanidine and anorthoclase and modeling of rock cooling paths. American Mineralogist: 76: 928-941.

Widder, W. (1991) Röntgentopographische Untersuchungen am Sanidin von Volkesfeld und Orthoklas von Madagaskar. Diplomarbeit an der Fakultät für Physik, Universität Karlsruhe, Karlsruhe, Germany.

Widder, W., Wondratscher, H., Fehlmann, M., and Klapper, H. (1994) X-ray topographic study of Eifel sanidine (Volkesfeld). Zeitschrift für Kristallographie: 209: 206-209.

Mineralogical Record (1995): 26: 222.

Kimata, M., Saito, S., Shimizu, M., Iida, I., and Tomoaki, M. (1996) Low-temperature crystal structures of orthoclase and sanidine. Neues Jahrbuch für Mineralogie, Abhandlungen: 171: 199-213.

Mineralien Welt (1999): 10(6): 40-44.

Ginibre, C., Wörner, G., and Kronz, A. (2004) Structure and dynamics of the Laacher See magma chamber (Eifel, Germany) from major and trace element zoning in sanidine: a cathodoluminescence and electron microprobe study. Journal of Petrology: 45: 2197-2224.

Internet Links for Sanidine

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

Localities for Sanidine

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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