Wilkinsonite
A valid IMA mineral species
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About Wilkinsonite
Formula:
Na2Fe2+4Fe3+2(Si6O18)O2
Colour:
Black
Lustre:
Vitreous
Hardness:
5
Specific Gravity:
3.89 (Calculated)
Crystal System:
Triclinic
Member of:
Name:
Named in 1990 by M.B. Duggan in honor of John Frederick George Wilkinson (10 October 1927, Bundaberg, Queensland, Australia - 8 October 2014, Sydney, New South Wales, Australia), professor of geology, University of New England, Australia. He was a specialist in the petrology of igneous rocks.
Unique Identifiers
Mindat ID:
4290
Long-form identifier:
mindat:1:1:4290:7
IMA Classification of Wilkinsonite
Approved
IMA Formula:
Na4(Fe2+8Fe3+4)O4[Si12O36]
Approval year:
1988
Classification of Wilkinsonite
9.DH.40
9 : SILICATES (Germanates)
D : Inosilicates
H : Inosilicates with 4-periodic single chains, Si4O12
9 : SILICATES (Germanates)
D : Inosilicates
H : Inosilicates with 4-periodic single chains, Si4O12
69.2.1a.8
69 : INOSILICATES Chains with Side Branches or Loops
2 : Chains with Side Branches or Loops with P>2
69 : INOSILICATES Chains with Side Branches or Loops
2 : Chains with Side Branches or Loops with P>2
14.20.4
14 : Silicates not Containing Aluminum
20 : Silicates of Fe and alkali metals
14 : Silicates not Containing Aluminum
20 : Silicates of Fe and alkali metals
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 |
|---|---|---|
| Wkn | 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 Wilkinsonite
Vitreous
Transparency:
Translucent, Opaque
Colour:
Black
Streak:
Brown
Hardness:
5 on Mohs scale
Tenacity:
Brittle
Fracture:
Conchoidal
Density:
3.89 g/cm3 (Calculated)
Optical Data of Wilkinsonite
Type:
Biaxial (+)
RI values:
nα = 1.79 nβ = 1.79 nγ = 1.90
Max. Birefringence:
δ = 0.110
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 biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
single
Pleochroism:
Strong
Comments:
X = olive-green;
Y = gray-brown;
Z = very dark brown.
Y = gray-brown;
Z = very dark brown.
Chemistry of Wilkinsonite
Mindat Formula:
Na2Fe2+4Fe3+2(Si6O18)O2
Element Weights:
Elements listed:
Common Impurities:
Ti,Zr,Al,Cr,Nb,Mn,Ni,Mg,Ca,K
Crystallography of Wilkinsonite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 10.3355(5) Å, b = 10.784(4) Å, c = 8.9142(4) Å
α = 105.048(3)°, β = 96.461(3)°, γ = 125.302(2)°
α = 105.048(3)°, β = 96.461(3)°, γ = 125.302(2)°
Ratio:
a:b:c = 0.958 : 1 : 0.827
Unit Cell V:
738.37 ų
Z:
2
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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CIF File Best | x | y | z | a | b | c
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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) |
|---|---|---|---|---|---|---|---|
| 0010476 | Wilkinsonite | Burt J B, Downs R T, Costin G (2007) Single-crystal X-ray refinement of wilkinsonite, Na2Fe2+4Fe3+2Si6O20. Acta Crystallographica E63 i122-i124 | ![]() | 2007 | Warrumbungle Volcano, central New South Wales, Australia | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.10 Å | (100) |
| 3.149 Å | (100) |
| 2.696 Å | (80) |
| 2.533 Å | (80) |
| 2.115 Å | (70) |
| 2.935 Å | (60) |
| 1.481 Å | (50) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 2: Planetesimal differentiation and alteration | 4.566-4.550 |
| 6 : Secondary asteroid phases | 4.566-4.560 |
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 9 : Lava/xenolith minerals (hornfels, sanidinite facies) | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Wilkinsonite
Place of Conservation of Type Material:
Petrological Museum, Bureau of Mineral Resources, Canberra, Australia, R29655.
Geological Setting of Type Material:
eruptive peralkaline trachyte
Associated Minerals at Type Locality:
Synonyms of Wilkinsonite
Other Language Names for Wilkinsonite
Relationship of Wilkinsonite to other Species
Member of:
Other Members of Aenigmatite Group:
| Aenigmatite | Na4[Fe2+10Ti2]O4[Si12O36] | Tric. 1 : P1 |
| Krinovite | Na2Mg4Cr3+2(Si6O18)O2 | Tric. 1 : P1 |
| 'UM1991-29-SiO:FeMgNa' | Na4(Mg5Fe3+7)O4[Si9Fe3+3O36] |
Common Associates
Associations Based on Photo Data:
| 1 photo of Wilkinsonite associated with Aegirine | NaFe3+Si2O6 |
| 1 photo of Wilkinsonite associated with 'Anorthoclase' | (Na,K)AlSi3O8 |
| 1 photo of Wilkinsonite associated with Sodalite | Na4(Si3Al3)O12Cl |
| 1 photo of Wilkinsonite associated with Aenigmatite | Na4[Fe2+10Ti2]O4[Si12O36] |
| 1 photo of Wilkinsonite associated with Arfvedsonite | NaNa2(Fe2+4Fe3+)Si8O22(OH)2 |
Related Minerals - Strunz-mindat Grouping
| 9.DH. | Devilliersite | Ca4Ca2Fe3+10O4[(Fe3+10Si2)O36] |
| 9.DH. | 'Gageite-2M' | (Mn,Mg,Zn)42Si16O54(OH)40 |
| 9.DH. | Bavsiite | Ba2V2O2[Si4O12] |
| 9.DH. | Yuzuxiangite | Sr3Fe3+(Si2O6)2(OH) · 3H2O |
| 9.DH. | Louisfuchsite | Ca2(Mg4Ti2)(Al4Si2)O20 |
| 9.DH.05 | Leucophanite | NaCaBeSi2O6F |
| 9.DH.10 | Ohmilite | Sr3(Ti,Fe3+)(Si4O12)(O,OH) · 2-3H2O |
| 9.DH.15 | Haradaite | SrVSi2O7 |
| 9.DH.15 | Suzukiite | BaVSi2O7 |
| 9.DH.20 | Shcherbakovite | (K,Ba)KNa(Ti,Nb)2(Si4O12)O2 |
| 9.DH.20 | Batisite | BaNaNaTi2(Si4O12)O2 |
| 9.DH.20 | Noonkanbahite | BaKNaTi2(Si4O12)O2 |
| 9.DH.25 | Taikanite | Sr3BaMn2+2(Si4O12)O2 |
| 9.DH.30 | Krauskopfite | BaSi2O5 · 3H2O |
| 9.DH.35 | Gageite | Mn21(Si4O12)2O3(OH)20 |
| 9.DH.35 | Balangeroite | (Mg,Fe2+,Fe3+,Mn2+)42Si16O54(OH)40 |
| 9.DH.40 | Kuratite | Ca2(Fe2+5Ti)O2[Si4Al2O18] |
| 9.DH.40 | Aenigmatite | Na4[Fe2+10Ti2]O4[Si12O36] |
| 9.DH.40 | Dorrite | Ca4(Mg3Fe3+9)O4(Si3Al8Fe3+O36) |
| 9.DH.40 | Serendibite | Ca4[Mg6Al6]O4[Si6B3Al3O36] |
| 9.DH.40 | Rhönite | Ca4[Mg8Fe3+2Ti2]O4[Si6Al6O36] |
| 9.DH.40 | Khesinite | Ca4(Mg3Fe3+9)O4(Fe3+9Si3)O36 |
| 9.DH.40 | 'UM1991-29-SiO:FeMgNa' | Na4(Mg5Fe3+7)O4[Si9Fe3+3O36] |
| 9.DH.40 | Høgtuvaite | Ca4[Fe2+6Fe3+6]O4[Si8Be2Al2O36] |
| 9.DH.40 | 'Leucorhönite' | Ca2(Mg,Fe3+,Al)6(Si,Al)6O20 |
| 9.DH.40 | Welshite | Ca4Mg9Sb3O4[Si6Be3AlFe2O36] |
| 9.DH.40 | Krinovite | Na2Mg4Cr3+2(Si6O18)O2 |
| 9.DH.40 | Makarochkinite | (Ca,Na)4[Fe2+8Fe3+2Ti2]O4[Si8Be2Al2O36] |
| 9.DH.45 | Sapphirine | Mg4(Mg3Al9)O4[Si3Al9O36] |
| 9.DH.50 | Khmaralite | (Mg,Al,Fe)16[(Al,Si,Be)12O36]O4 |
| 9.DH.55 | 'UM1988-26-SiO:AlMg' | Mg4Al2O[Si3Al2O15] |
| 9.DH.55 | Surinamite | (Mg,Fe)3Al4BeSi3O16 |
| 9.DH.60 | Deerite | Fe2+6Fe3+3(Si6O17)O3(OH)5 |
| 9.DH.65 | Taneyamalite | (Na,Ca)Mn2+12(Si,Al)12(O,OH)44 |
| 9.DH.65 | Howieite | Na(Fe2+,Fe3+,Al,Mg)12(Si6O17)2(O,OH)10 |
| 9.DH.70 | Johninnesite | Na2Mn2+9Mg7(OH)8[AsO4]2[Si6O17]2 |
| 9.DH.75 | Agrellite | NaCa2Si4O10F |
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 Wilkinsonite
mindat.org URL:
https://www.mindat.org/min-4290.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Wilkinsonite
Reference List:
Duggan, Morris B. (1990) Wilkinsonite, Na2Fe2+4Fe3+2Si6O20, a new member of the aenigmatite group from the Warrumbungle Volcano, New South Wales, Australia. American Mineralogist, 75 (5-6) 694-701
Gaeta, Mario, Mottana, Annibale (1991) Phase relations of aenigmatite minerals in a syenitic ejectum, wonchi volcano, Ethiopia. Mineralogical Magazine, 55 (381) 529-534 doi:10.1180/minmag.1991.055.381.05
Jensen, B. B. (1996) Solid solution among members of the aenigmatite group. Mineralogical Magazine, 60 (403) 982-986 doi:10.1180/minmag.1996.060.403.14
Kunzmann, Thomas (1999) The aenigmatite-rhönite mineral group. European Journal of Mineralogy, 11 (4) 743-756 doi:10.1127/ejm/11/4/0743
Localities for Wilkinsonite
Showing 6 localities.
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.
Australia (TL) | |
| Duggan (1990) +1 other reference |
Brazil | |
| Guarino et al. (2021) |
Czech Republic | |
| Jirasek et al. (2026) |
Ethiopia | |
| Gaeta et al. (1991) +1 other reference |
Mongolia | |
| Pavel M. Kartashov (n.d.) |
Yemen | |
| Zolensky et al. (2003) |
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The
Warrumbungles, New South Wales, Australia