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Leucite

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Formula:
K(AlSi2O6)
System:
Tetragonal
Colour:
White, grey
Hardness:
5½ - 6
Name:
From the Greek "leucos," for white, in allusion to its common colour.
Leucite is common in some volcanic rocks in which it crystallises with a cubic crystal structure at high temperature (ca. 900°C). Upon cooling to 700-600°C, it transforms into a tetragonal modification which is stable at room temperature, and forms characteristic polysynthetic twin lamellae. The transformation is reversible.

The mineral is usually included as a feldspathoid by petrologists, as it is a common primary rock-forming mineral in some high-potassium rocks but, despite being anhydrous, structurally it also has a topological relation to zeolites, especially analcime, and thus is typically included in that family also.

Visit gemdat.org for gemological information about Leucite.

Classification of Leucite

Approved, 'Grandfathered' (first described prior to 1959)
9.GB.05

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H2O; zeolite family
B : Chains of single connected 4-membered rings
76.2.2.1

76 : TECTOSILICATES Al-Si Framework
2 : Al-Si Framework Feldspathoids and related species
16.3.4

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

Occurrences of Leucite

Geological Setting:
Potasium rich mafic and ultramafic lavas.

Physical Properties of Leucite

Vitreous
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
White, grey
Hardness (Mohs):
5½ - 6
Tenacity:
Brittle
Cleavage:
Poor/Indistinct
Very poor om {110}
Fracture:
Conchoidal
Density:
2.45 - 2.5 g/cm3 (Measured)    2.46 g/cm3 (Calculated)

Crystallography of Leucite

Crystal System:
Tetragonal
Class (H-M):
4/m - Dipyramidal
Space Group:
I41/a
Cell Parameters:
a = 13.056Å, c = 13.751Å
Ratio:
a:c = 1 : 1.053
Unit Cell Volume:
V 2,343.98 ų (Calculated from Unit Cell)
Z:
16
Morphology:
Euhedral pseudocubic crystals
Twinning:
Common, repeated on {110} and {101}, from two complex displacive phase transformations during cooling.

Crystallographic forms of Leucite

Crystal Atlas:
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Click on an icon to view
Leucite no.2 - Goldschmidt (1913-1926)
Leucite no.4 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation
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 Leucite

Type:
Uniaxial (+)
RI values:
nω = 1.508 nε = 1.509
Max Birefringence:
δ = 0.001
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Comments:
May be anomalously biaxial.

Chemical Properties of Leucite

Formula:
K(AlSi2O6)
All elements listed in formula:
Common Impurities:
Ti,Fe,Mg,Ca,Ba,Na,Rb,Cs,H2O

Relationship of Leucite to other Species

Other Members of Group:
Cancrinite(Na,Ca,☐)8(Al6Si6O24)(CO3,SO4)2 · 2H2O
Haüyne(Na,Ca)4-8(Al6Si6O24)(SO4,S,Cl)1-2
Nepheline(Na,K)AlSiO4
NoseanNa8(Al6Si6O24)(SO4) · H2O
SodaliteNa8(Al6Si6O24)Cl2
Sodalite Group
9.GB.05Ammonioleucite(NH4,K)(AlSi2O6)
9.GB.05AnalcimeNa(AlSi2O6) · H2O
9.GB.05HsianghualiteCa3Li2(Be3Si3O12)F2
9.GB.05LithositeK6Al4Si8O25 · 2H2O
9.GB.05Pollucite(Cs,Na)2(Al2Si4O12) · 2H2O
9.GB.05WairakiteCa(Al2Si4O12) · 2H2O
9.GB.05KirchhoffiteCs(BSi2O6)
9.GB.10LaumontiteCaAl2Si4O12 · 4H2O
9.GB.15YugawaraliteCaAl2Si6O16 · 4H2O
9.GB.20RoggianiteCa2Be(OH)2Al2Si4O13 · 2.5H2O
9.GB.25GoosecreekiteCa[Al2Si6O16] · 5H2O
9.GB.30Montesommaite(K,Na)9Al9Si23O64 · 10H2O
9.GB.35ParthéiteCa2(Si4Al4) O15 (OH)2•4H2O
16.3.1LithositeK6Al4Si8O25 · 2H2O
16.3.2KaliophiliteKAlSiO4
16.3.3KalsiliteKAlSiO4
16.3.5MicroclineK(AlSi3O8)
16.3.6OrthoclaseK(AlSi3O8)
16.3.7SanidineK(AlSi3O8)
16.3.8MuscoviteKAl2(AlSi3O10)(OH)2

Other Names for Leucite

Name in Other Languages:
Dutch:Leuciet
Hebrew:לוסיט
Italian:Leucite
Polish:Leucyt
Russian:Лейцит
Simplified Chinese:白榴石
Spanish:Leucita
Swedish:Leucit

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 Leucite

Reference List:
Klaproth, M.H. (1797): Untersuchung des Leucit, Beiträge zur chemischen Kenntniss der Mineralkörper, Zweiter Band, Rottmann Berlin, 39-59

von Buch, L. (1800): Über die Formation des Leucits. Annalen der Physik, Vol. 6, 53-66.

Onorato, E. (1938): Ricerche roentgenografiche sulla leucite. Periodico di Mineralogia – Roma, 85-97.

American Mineralogist (1976): 61: 108-115.

Mineralogical Record: 30: 5-6.

Hatch, D.M., Ghose, S., Stokes, H.T. (1990): Phase transitions in leucite, KAlSi2O6. Physics and Chemistry of Minerals, 17, 220–227.

American Mineralogist (1993): 78: 486.

Phillips, B.L. and Kirkpatrick, R.J. (1994) Short-range Al-Si order in leucite and analcime: determination of the configurational entropy from 27Al and variable-temperature 29Si NMR spectroscopy of leucite, its Cs- and Rb-exchanged derivatives, and analcime. American Mineralogist: 79: 1025-1031.

Internet Links for Leucite

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

Localities for Leucite

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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