Stillwellite-(Ce)
A valid IMA mineral species - grandfathered
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About Stillwellite-(Ce)
Frank L. Stillwell
Formula:
(Ce,La,Ca)BSiO5
Colour:
Pale violet-gray, light pink, brownish yellow, orange
Lustre:
Resinous
Hardness:
6½
Specific Gravity:
4.57 - 4.60
Crystal System:
Trigonal
Name:
Named stillwellite in 1955 by J. McAndrew and T.R. Scott in honor of Frank Leslie Stillwell (27 June 1888, Hawthorn, Australia - 8 February 1963, Melbourne, Australia), Australian ore mineralogist with CSIRO and an Antarctic explorer. He worked on Broken Hill and Kalgoorlie gold field, among other places. The suffix/modifier was added in 1987 to conform to the Levinson rule for species with essential REE, in this case predominantly cerium.
A cerium-dominant nesosilicate borosilicate. The cerium analogue of stillwellite-(La).
Originally described in 1955 from the uranium deposit Mary Kathleen Mine in Australia in 1955 (McAndrew & Scott, 1955). Gay (1957) did some XRD analysis and confirmed the chemistry as a rare-earth-element borosilicate. The crystal structure was solved by Voronkov & Pyatenko (1967), and further refined by Burns et al. (1993).
Originally described in 1955 from the uranium deposit Mary Kathleen Mine in Australia in 1955 (McAndrew & Scott, 1955). Gay (1957) did some XRD analysis and confirmed the chemistry as a rare-earth-element borosilicate. The crystal structure was solved by Voronkov & Pyatenko (1967), and further refined by Burns et al. (1993).
Unique Identifiers
Mindat ID:
3788
Long-form identifier:
mindat:1:1:3788:0
Similar Names
| Stillwellite | A synonym | |
| Stillwellite-(La) | A valid IMA mineral species - pending publication | LaBSiO5 |
IMA Classification of Stillwellite-(Ce)
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ce3+BSiO5
First published:
1955
Classification of Stillwellite-(Ce)
9.AJ.25
9 : SILICATES (Germanates)
A : Nesosilicates
J : Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO4
9 : SILICATES (Germanates)
A : Nesosilicates
J : Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO4
54.2.3.2
54 : NESOSILICATES Borosilicates and Some Beryllosilicates
2 : Borosilicates and Some Beryllosilicates with B in [4] coordination
54 : NESOSILICATES Borosilicates and Some Beryllosilicates
2 : Borosilicates and Some Beryllosilicates with B in [4] coordination
17.5.18
17 : Silicates Containing other Anions
5 : Borosilicates
17 : Silicates Containing other Anions
5 : Borosilicates
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 |
|---|---|---|
| Swl-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 Stillwellite-(Ce)
Resinous
Transparency:
Transparent, Translucent
Colour:
Pale violet-gray, light pink, brownish yellow, orange
Streak:
White
Hardness:
6½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Imperfect/Fair
One imperfect
One imperfect
Fracture:
Conchoidal
Density:
4.57 - 4.60 g/cm3 (Measured) 4.67 g/cm3 (Calculated)
Optical Data of Stillwellite-(Ce)
Type:
Uniaxial (+)
RI values:
nω = 1.765 nε = 1.78
Max. Birefringence:
δ = 0.015
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:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Comments:
to biaxial (+)
Chemistry of Stillwellite-(Ce)
Mindat Formula:
(Ce,La,Ca)BSiO5
Element Weights:
Chemical Analysis
Oxide wt%:
| 1 | 2 | 3 | |
|---|---|---|---|
| SiO2 | 22.40 % | 22.06 % | |
| B2O3 | 12.23 % | 13.46 % | |
| Al2O3 | 0.42 % | ||
| Y2O3 | 0.74 % | 0.28 % | |
| La2O3 | 27.95 % | 19.12 % | 25 % |
| Ce2O3 | 33.15 % | 30.82 % | 30 % |
| Fe2O3 | 0.18 % | ||
| MgO | 0.06 % | ||
| CaO | 0.95 % | 0.34 % | |
| F | 0.30 % | ||
| H2O+ | 0.85 % | ||
| H2O- | 0.10 % | ||
| P2O5 | 0.67 % | ||
| UO2 | 0.22 % | ||
| ThO2 | 5.41 % | 0.5 % | |
| Pr2O3 | 1.82 % | 1 % | |
| Nd2O3 | 5.36 % | 2 % | |
| Sm2O3 | 0.34 % | 0.25 % | |
| Total: | 100 % | 99.23 % | 58.75 % |
Sample references:
| ID | Type | Locality | Reference | Notes |
|---|---|---|---|---|
| 1 | Type Specimen | Mary Kathleen Mine, Mary Kathleen district, Rosebud Station, Cloncurry Shire, Queensland, Australia | Calculated to 100.00% after removal of very small amounts of uraninite and apatite determined by separate analysis. | |
| 2 | Vico volcanic complex, Viterbo Province, Lazio, Italy | B2O3 calculated from stolchiometry. | ||
| 3 | Langesundsfjorden, Norway | Partial semiquantitative XRF analysis |
Crystallography of Stillwellite-(Ce)
Crystal System:
Trigonal
Class (H-M):
3 - Pyramidal
Space Group:
P31
Cell Parameters:
a = 6.843(2) Å, c = 6.701(1) Å
Ratio:
a:c = 1 : 0.979
Unit Cell V:
271.75 ų (Calculated from Unit Cell)
Z:
3
Twinning:
Observed about [100].
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0018728 | Stillwellite-(Ce) | Callegari A, Giuseppetti G, Mazzi F, Tadini C (1992) The refinement of the crystal structure of stillwellite: RE[BSiO5] Neues Jahrbuch fur Mineralogie, Monatshefte 1992 49-57 | 1992 | Bassano Romano, Viterbo, Italy | 0 | 293 | |
| 0018733 | Stillwellite-(Ce) | Voronkov A A, Pyatenko Y A (1967) X-ray diffraction study of the atomic structure of stillwellite CeBO[SiO4] Soviet Physics Crystallography 12 214-220 | 1967 | Soviet | 0 | 293 | |
| 0005293 | Stillwellite-(Ce) | Burns P C, Hawthorne F C, MacDonald D J, Ventura G D, Parodi G (1993) The crystal structure of stillwellite The Canadian Mineralogist 31 147-152 |  | 1993 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| - Å | () |
Comments:
Data collected by Gay (1957).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 31 : Thermally altered carbonate, phosphate, and iron formations | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Stillwellite-(Ce)
General Appearance of Type Material:
As flat rhombohedral crystals, to 5 mm. Also massive.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 113038.
Geological Setting of Type Material:
A metasomatic replacement of metamorphosed calcareous sediments.
Associated Minerals at Type Locality:
Synonyms of Stillwellite-(Ce)
Stillwellite (in part)
Other Language Names for Stillwellite-(Ce)
Dutch:Stillwelliet-(Ce)
German:Stillwellit-(Ce)
Russian:Стиллуэллит-(Ce)
Simplified Chinese:菱硼硅铈矿
Traditional Chinese:菱硼矽鈰礦
Common Associates
Associations Based on Photo Data:
| 7 photos of Stillwellite-(Ce) associated with Quartz | SiO2 |
| 6 photos of Stillwellite-(Ce) associated with Fluorapophyllite-(K) | KCa4(Si8O20)(F,OH) · 8H2O |
| 4 photos of Stillwellite-(Ce) associated with Clinochlore | Mg5Al(AlSi3O10)(OH)8 |
| 2 photos of Stillwellite-(Ce) associated with Calcite | CaCO3 |
| 2 photos of Stillwellite-(Ce) associated with Polylithionite | KLi2Al(Si4O10)(F,OH)2 |
| 2 photos of Stillwellite-(Ce) associated with Pectolite | NaCa2Si3O8(OH) |
| 1 photo of Stillwellite-(Ce) associated with Vicanite-(Ce) | (Ca,Ce,La,Th)15As5+(As3+0.5,Na0.5)Fe3+Si6B4O40F7 |
| 1 photo of Stillwellite-(Ce) associated with Gonnardite | (Na,Ca)2(Si,Al)5O10 · 3H2O |
| 1 photo of Stillwellite-(Ce) associated with Thorite | Th(SiO4) |
| 1 photo of Stillwellite-(Ce) associated with Aegirine | NaFe3+Si2O6 |
Related Minerals - Strunz-mindat Grouping
| 9.AJ. | Hingganite-(Nd) | Nd2◻Be2Si2O8(OH)2 |
| 9.AJ. | Arrheniusite-(Ce) | CaMg[(Ce7Y3)Ca5](SiO4)4(Si2B3AsO18)(BO3)F11 |
| 9.AJ.05 | Ominelite | (Fe2+,Mg)(Al,Fe3+)3(SiO4)(BO3)O2 |
| 9.AJ.05 | Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| 9.AJ.10 | Dumortierite | Al(Al2O)(Al2O)2(SiO4)3(BO3) |
| 9.AJ.10 | Nioboholtite | (Nb0.6◻0.4)Al6BSi3O18 |
| 9.AJ.10 | Titanoholtite | (Ti0.75◻0.25)Al6BSi3O18 |
| 9.AJ.10 | Holtite | (Ta0.6◻0.4)Al6BSi3O18(O,OH)2.25 |
| 9.AJ.10 | Magnesiodumortierite | Mg(Al2OH)(Al2O)2(SiO4)3(BO3) |
| 9.AJ.15 | Garrelsite | Ba3NaSi2B7O16(OH)4 |
| 9.AJ.20 | 'Muromontite' | near Be2FeY2Si3O12 |
| 9.AJ.20 | Gadolinite-(Nd) | Nd2Fe2+Be2O2(SiO4)2 |
| 9.AJ.20 | Datolite | CaB(SiO4)(OH) |
| 9.AJ.20 | Melanocerite-(Ce) | (Ce,Ca)5(SiO4,BO4)3(OH,O) |
| 9.AJ.20 | Gadolinite-(Ce) | (Ce,La,Nd,Y)2Fe2+Be2Si2O10 |
| 9.AJ.20 | Gadolinite-(Y) | Y2Fe2+Be2Si2O10 |
| 9.AJ.20 | 'Unnamed (OH-analogue of Gadolinite-(Y))' | (Y,Ca)2(Fe,◻)Be2Si2O8(OH,O)2 |
| 9.AJ.20 | Hingganite-(Ce) | (Ce,REE)2(◻,Fe2+)Be2[SiO4]2(OH)2 |
| 9.AJ.20 | Hingganite-(Y) | (Y,REE,Ca)2(◻,Fe2+)Be2[SiO4]2(OH)2 |
| 9.AJ.20 | Hingganite-(Yb) | (Yb,Y,REE)2◻Be2[SiO4]2(OH)2 |
| 9.AJ.20 | Homilite | Ca2(Fe2+,Mg)B2Si2O10 |
| 9.AJ.20 | 'Minasgeraisite-(Y)' | (Ca2Y2)◻2(Be2B2)[SiO4]4(OH)4 |
| 9.AJ.20 | Calcybeborosilite-(Y) | (Y,Ca)2(◻,Fe2+)(B,Be)2[SiO4]2(OH,O)2 |
| 9.AJ.25 | Stillwellite-(La) | LaBSiO5 |
| 9.AJ.30 | Cappelenite-(Y) | Ba(Y,Ce)6Si3B6O24F2 |
| 9.AJ.35 | Laptevite-(Ce) | Ca6(Fe2+,Mn2+)Y3REE7(SiO4)3(PO4)(B3Si3O18)(BO3)F11 |
| 9.AJ.35 | Proshchenkoite-(Y) | Ca(Y,REE,Ca,Na,Mn)15Fe2+(P,Si)Si6B3O34F14 |
| 9.AJ.35 | Okanoganite-(Y) | (Na,Ca)3(Y,Ce)12Si6B2O27F14 |
| 9.AJ.35 | Hundholmenite-(Y) | (Y,REE,Ca,Na)15(Al,Fe3+)(CaxAs3+1-x)(Si,As5+)Si6B3(O,F)48 |
| 9.AJ.35 | Vicanite-(Ce) | (Ca,Ce,La,Th)15As5+(As3+0.5,Na0.5)Fe3+Si6B4O40F7 |
| 9.AJ.40 | Jadarite | LiNaSiB3O7(OH) |
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 Stillwellite-(Ce)
mindat.org URL:
https://www.mindat.org/min-3788.html
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References for Stillwellite-(Ce)
Reference List:
McAndrew, J., Scott, T. R. (1955) Stillwellite, a New Rare-Earth Mineral from Queensland. Nature, 176 (4480). 509-510 doi:10.1038/176509b0
Gay, P. (1957) An X-ray investigation of some rare-earth silicates: cerite, lessingite, beckelite, britholite, and stillwellite. Mineralogical Magazine and Journal of the Mineralogical Society, 31 (237). 455-468 doi:10.1180/minmag.1957.031.237.04
Neumann, Henrich; Bergstøl, Sveinung; Nilssen, Borghild (1966) Contributions to the mineralogy of Norway. No. 34. Stillwellite in the Langesundfjord nepheline syenite pegmatite dykes. Norsk Geologisk Tidsskrift [Norwegian Journal of Geology], 46 (3). p.327-334.
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
Krzhizhanovskaya, M.G., Kopylova, Yu.O., Obozova, E.D., Zalesskii, V.G., Lushnikov, S.G., Gorelova, L.A., Shilovskikh, V.V., Ugolkov, V.L., Britvin, S.N., Pekov, I.V. (2023) Thermal evolution of stillwellite, CeBSiO5, a natural prototype for a family of NLO-active materials. Journal of Solid State Chemistry, 318. 123786 doi:10.1016/j.jssc.2022.123786
Localities for Stillwellite-(Ce)
Showing 30 localities.
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The Locality List
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- This locality has estimated coordinates.
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- Good crystals or important locality for species.
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(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.
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A/S Granit Quarry, Tuften, Tvedalen, Larvik Commune, Vestfold, Norway