Ilímaussite-(Ce)
A valid IMA mineral species
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About Ilímaussite-(Ce)
Formula:
(Na,K)7-8(Ba,K)10Ce5(Nb,Ti)6(Si3O9)4(Si9O18)O6(O,OH)24
the formula associated with crystal structure refinement: (Ba,Na)10K3Na4.5Ce5(Nb,Ti)6[Si12O36][Si9O18(O,OH)24]O6
Colour:
Brownish yellow
Lustre:
Resinous
Hardness:
4
Specific Gravity:
3.6
Crystal System:
Trigonal
Name:
Originally named ilimaussite for the type locality at Nakalak (Nakalaq) Mountain, Ilimaussaq complex, Narsaq, Kitaa (West Greenland) Province, Greenland. The suffix/modifier was added in 1987 to conform to the Levinson rule for species with essential REE, indicating, in this case, a predominance of cerium. The diacritic was added in 2008.
Unique combination of elements. One of a few minerals with dominant Ce and Nb, a feature shared, e.g., with nacareniobsite-(Ce). A K,Ti-analogue is also known: Unnamed (K-Ti analogue of ilímaussite-(Ce)).
The structure is based on 3 pairs of (001) silicate sheets, that sandwich:
- CeO6 trigonal prisms + Na cations (A layer, with 2 equivalent silicate sheets comprising non-interconnected six-membered rings)
- NbO6 octahedra + Ba + K (O layer; the octahedra share corners with silicate tetrahedra)
- CeO6 trigonal prisms (A' layer, with 50% Si occupancy -> disored of basal oxygen atoms)
The layer sequence is AOA'O. Somewhat related to diversilite-(Ce).
The structure is based on 3 pairs of (001) silicate sheets, that sandwich:
- CeO6 trigonal prisms + Na cations (A layer, with 2 equivalent silicate sheets comprising non-interconnected six-membered rings)
- NbO6 octahedra + Ba + K (O layer; the octahedra share corners with silicate tetrahedra)
- CeO6 trigonal prisms (A' layer, with 50% Si occupancy -> disored of basal oxygen atoms)
The layer sequence is AOA'O. Somewhat related to diversilite-(Ce).
Name Encoding
ASCII-7:
Ilimaussite-(Ce)
Unique Identifiers
Mindat ID:
2010
Long-form identifier:
mindat:1:1:2010:3
IMA Classification of Ilímaussite-(Ce)
Approved
IMA status notes:
Renamed by the IMA
IMA Formula:
(Ba,Na)10K3Na4.5Ce3+5(Nb5+,Ti4+)6O6(Si12O36)(Si9O18)(O,OH)24
Approval year:
1965
First published:
1968
Classification of Ilímaussite-(Ce)
9.CB.15
9 : SILICATES (Germanates)
C : Cyclosilicates
B : [Si3O9]6- 3-membered single rings, with insular complex anions
9 : SILICATES (Germanates)
C : Cyclosilicates
B : [Si3O9]6- 3-membered single rings, with insular complex anions
78.7.4.1
78 : Unclassified Silicates
7 :
78 : Unclassified Silicates
7 :
17.8.14
17 : Silicates Containing other Anions
8 : Silicates with niobate or tantalate
17 : Silicates Containing other Anions
8 : Silicates with niobate or tantalate
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Ilí-Ce | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Ilímaussite-(Ce)
Resinous
Transparency:
Transparent, Translucent
Colour:
Brownish yellow
Streak:
White
Hardness:
4 on Mohs scale
Comment:
ca. 4
Fracture:
Conchoidal
Density:
3.6 g/cm3 (Measured) 3.7 g/cm3 (Calculated)
Optical Data of Ilímaussite-(Ce)
Type:
Uniaxial (+)
RI values:
nω = 1.689 nε = 1.695
Max. Birefringence:
δ = 0.006
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate
Chemistry of Ilímaussite-(Ce)
Mindat Formula:
(Na,K)7-8(Ba,K)10Ce5(Nb,Ti)6(Si3O9)4(Si9O18)O6(O,OH)24
the formula associated with crystal structure refinement: (Ba,Na)10K3Na4.5Ce5(Nb,Ti)6[Si12O36][Si9O18(O,OH)24]O6
the formula associated with crystal structure refinement: (Ba,Na)10K3Na4.5Ce5(Nb,Ti)6[Si12O36][Si9O18(O,OH)24]O6
Element Weights:
Crystallography of Ilímaussite-(Ce)
Crystal System:
Trigonal
Class (H-M):
32 - Trapezohedral
Space Group:
R32
Cell Parameters:
a = 10.770(3) Å, c = 61.05(2) Å
Ratio:
a:c = 1 : 5.669
Unit Cell V:
6,132.64 ų (Calculated from Unit Cell)
Twinning:
Polysynthetic.
Comment:
Previously reported to be hexagonal
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.67 Å | (100) |
| 3.25 Å | (60) |
| 3.12 Å | (50) |
| 2.98 Å | (40) |
| 2.24 Å | (30) |
| 2.50 Å | (20) |
| 2.022 Å | (20 broad) |
Comments:
Ilímaussaq complex, Greenland. The data are from the type description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Ilímaussite-(Ce)
General Appearance of Type Material:
Lamellar aggregates, up to 1.5 cm.
Place of Conservation of Type Material:
No designated type specimen.
Geological Setting of Type Material:
Hydrothermal ussingite-analcime vein cutting sodalite syenite.
Associated Minerals at Type Locality:
Synonyms of Ilímaussite-(Ce)
Other Language Names for Ilímaussite-(Ce)
Common Associates
Associations Based on Photo Data:
| 3 photos of Ilímaussite-(Ce) associated with Ussingite | Na2AlSi3O8OH |
| 2 photos of Ilímaussite-(Ce) associated with Chkalovite | Na2BeSi2O6 |
Related Minerals - Strunz-mindat Grouping
| 9.CB.05 | Roeblingite | Pb2Ca6Mn2+(Si3O9)2(SO4)2(OH)2 · 4H2O |
| 9.CB.10 | Diversilite-(Ce) | Na2(Ba,K)6Fe2+Ce2Ti3(Si3O9)3(HSiO4)3(OH,H2O)9 |
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.
Internet Links for Ilímaussite-(Ce)
mindat.org URL:
https://www.mindat.org/min-2010.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Ilímaussite-(Ce)
Reference List:
Nickel, Ernest H., Mandarino, Joseph A. (1987) Procedures involving the IMA Commission on New Minerals and Mineral Names and guidelines on mineral nomenclature. American Mineralogist, 72 (9-10) 1031-1042
Jambor, John L., Roberts, Andrew C. (2005) New Mineral Names. American Mineralogist, 90 (1) 271-275 doi:10.2138/am.2005.429
Localities for Ilímaussite-(Ce)
Showing 4 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and 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).
All localities listed without proper references should be considered as questionable.
Greenland | |
| Petersen (2001) |
| Semenov et al. (1968) |
Russia | |
| [World of Stones 95:5-6 (but probably actually Diversilite-) |
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Taseq Slope, Ilímaussaq complex, Kujalleq, Greenland