Willemseite
A valid IMA mineral species
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About Willemseite
Johannes Willemse
Formula:
Ni3Si4O10(OH)2
Colour:
Light green
Lustre:
Waxy, Greasy
Hardness:
2
Specific Gravity:
3.31
Crystal System:
Monoclinic
Member of:
Name:
Named after Johannes Willemse (1909, Harrismith District, Orange Free State - 1967), Professor of Geology, University of Pretoria (South Africa). He was an authority on layered mafic intrusions and, in particular, on the Bushveld Igneous Complex.
Unique Identifiers
Mindat ID:
4293
Long-form identifier:
mindat:1:1:4293:8
Similar Names
| Williamsite | A variety of Antigorite | Mg3(Si2O5)(OH)4 |
IMA Classification of Willemseite
Approved
IMA Formula:
Ni2+3Si4O10(OH)2
First published:
1968
Classification of Willemseite
9.EC.05
9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
71.2.1.4
71 : PHYLLOSILICATES Sheets of Six-Membered Rings
2 : Sheets of 6-membered rings with 2:1 layers
71 : PHYLLOSILICATES Sheets of Six-Membered Rings
2 : Sheets of 6-membered rings with 2:1 layers
14.26.4
14 : Silicates not Containing Aluminum
26 : Silicates of Ni
14 : Silicates not Containing Aluminum
26 : Silicates of Ni
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Wls | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Wls | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30 |
Physical Properties of Willemseite
Waxy, Greasy
Transparency:
Translucent
Colour:
Light green
Hardness:
2 on Mohs scale
Cleavage:
Perfect
{001}
{001}
Density:
3.31(1) g/cm3 (Measured) 3.348 g/cm3 (Calculated)
Optical Data of Willemseite
Type:
Biaxial (-)
RI values:
nα = 1.600(2) nβ = 1.652(2) nγ = 1.655
2V:
Measured: 27° (2), Calculated: 26°
Max. Birefringence:
δ = 0.055
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:
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.
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.
Dispersion:
r < v, weak
Pleochroism:
Non-pleochroic
Chemistry of Willemseite
Mindat Formula:
Ni3Si4O10(OH)2
Element Weights:
Elements listed:
Common Impurities:
Al,Fe,Co,Ca,H2O
Crystallography of Willemseite
Crystal System:
Monoclinic
Cell Parameters:
a = 5.316(2) Å, b = 9.149(3) Å, c = 18.994(6) Å
β = 99.96(6)°
β = 99.96(6)°
Ratio:
a:b:c = 0.581 : 1 : 2.076
Unit Cell V:
909.85 ų
Z:
4
Comment:
Point Group: m or 2/m:; Space Group: Cc or C2/c:
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.40 Å | (100) |
| 3.12 Å | (28) |
| 2.503 Å | (23) |
| 4.57 Å | (16) |
| 2.245 Å | (8) |
| 1.524 Å | (7) |
| 3.55 Å | (3) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] |
Type Occurrence of Willemseite
General Appearance of Type Material:
fine grained massive
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 132464, 132465.
Associated Minerals at Type Locality:
Synonyms of Willemseite
Other Language Names for Willemseite
Relationship of Willemseite to other Species
Member of:
Other Members of Pyrophyllite-Talc Group:
| Ferripyrophyllite | Fe3+Si2O5(OH) | Mon. 2/m |
| Minnesotaite | Fe2+3Si4O10(OH)2 | Tric. 1 : P1 |
| Pyrophyllite | Al2Si4O10(OH)2 | Tric. 1 |
| Talc | Mg3Si4O10(OH)2 | Tric. 1 : P1 |
Common Associates
Associations Based on Photo Data:
| 8 photos of Willemseite associated with Trevorite | Ni2+Fe3+2O4 |
| 6 photos of Willemseite associated with Falcondoite | (Ni,Mg)4Si6O15(OH)2 · 6H2O |
| 2 photos of Willemseite associated with Tredouxite | NiSb2O6 |
| 1 photo of Willemseite associated with Népouite | Ni3Si2O5(OH)4 |
| 1 photo of Willemseite associated with Pecoraite | Ni3(Si2O5)(OH)4 |
| 1 photo of Willemseite associated with 'Chrysoprase' |
Related Minerals - Strunz-mindat Grouping
| 9.EC. | Meifuite | KFe6(Si7Al)O19(OH)4Cl2 |
| 9.EC. | Balestraite | KLi2V5+Si4O12 |
| 9.EC.05 | Talc | Mg3Si4O10(OH)2 |
| 9.EC.05 | Minnesotaite | Fe2+3Si4O10(OH)2 |
| 9.EC.9.EC. | Voloshinite | Rb(LiAl1.5◻0.5)(Al0.5Si3.5)O10F2 |
| 9.EC.10 | Fluorluanshiweiite | KLiAl1.5(Si3.5Al0.5)O10F2 |
| 9.EC.10 | Garmite | CsLiMg2(Si4O10)F2 |
| 9.EC.10 | Gorbunovite | CsLi2(Ti,Fe)Si4O10(F,OH,O)2 |
| 9.EC.10 | Ferripyrophyllite | Fe3+Si2O5(OH) |
| 9.EC.10 | Manganiceladonite | K(MgMn3+◻)(Si4O10)(OH)2 |
| 9.EC.10 | Luanshiweiite | KLiAl1.5(Si3.5Al0.5)O10(OH)2 |
| 9.EC.10 | Pyrophyllite | Al2Si4O10(OH)2 |
| 9.EC.15 | Paragonite | NaAl2(AlSi3O10)(OH)2 |
| 9.EC.15 | Ferroaluminoceladonite | K(Fe2+Al◻)(Si4O10)(OH)2 |
| 9.EC.15 | Nanpingite | CsAl2(AlSi3O10)(OH,F)2 |
| 9.EC.15 | Ferroceladonite | K(Fe2+Fe3+◻)(Si4O10)(OH)2 |
| 9.EC.15 | Ganterite | Ba0.5(Na,K)0.5Al2(Si2.5Al1.5)O10(OH)2 |
| 9.EC.15 | Kreiterite | CsLi2Fe3+(Si4O10)F2 |
| 9.EC.15 | Roscoelite | KV3+2(AlSi3O10)(OH)2 |
| 9.EC.15 | Aluminoceladonite | K(MgAl◻)(Si4O10)(OH)2 |
| 9.EC.15 | Tobelite | (NH4)Al2(AlSi3O10)(OH)2 |
| 9.EC.15 | Tainiolite | KLiMg2(Si4O10)F2 |
| 9.EC.15 | Celadonite | K(MgFe3+◻)(Si4O10)(OH)2 |
| 9.EC.15 | Chromceladonite | K(MgCr◻)(Si4O10)(OH)2 |
| 9.EC.15 | Montdorite | KFe2+1.5Mn2+0.5Mg0.5Si4O10(F,OH)2 |
| 9.EC.15 | Chromphyllite | KCr2(AlSi3O10)(OH)2 |
| 9.EC.15 | Boromuscovite | KAl2(BSi3O10)(OH)2 |
| 9.EC.15 | 'UM1988-22-SiO:AlCaFFeHKLiMg' | KLiMgAl2Si3O10F2 |
| 9.EC.15 | Chernykhite | (Ba,Na)(V3+,Al,Mg)2((Si,Al)4O10)(OH)2 |
| 9.EC.15 | Muscovite | KAl2(AlSi3O10)(OH)2 |
| 9.EC.20 | Masutomilite | K(LiAlMn2+)[AlSi3O10]F2 |
| 9.EC.20 | Oxyphlogopite | K(Mg,Ti,Fe)3[(Si,Al)4O10](O,F)2 |
| 9.EC.20 | 'Chloroferrokinoshitalite' | (Ba,K)(Fe2+,Mg)3(Al2Si2O10)(Cl,OH,F)2 |
| 9.EC.20 | Siderophyllite | KFe2+2Al(Al2Si2O10)(OH)2 |
| 9.EC.20 | Sokolovaite | CsLi2Al(Si4O10)F2 |
| 9.EC.20 | Hendricksite | KZn3(Si3Al)O10(OH)2 |
| 9.EC.20 | Tetraferriphlogopite | KMg3(Si3Fe3+)O10(OH)2 |
| 9.EC.20 | Fluorannite | KFe2+3(Si3Al)O10F2 |
| 9.EC.20 | Aspidolite | NaMg3(AlSi3O10)(OH)2 |
| 9.EC.20 | Suhailite | (NH4)Fe2+3(AlSi3O10)(OH)2 |
| 9.EC.20 | Ephesite | NaLiAl2(Al2Si2O10)(OH)2 |
| 9.EC.20 | Norrishite | KLiMn3+2(Si4O10)O2 |
| 9.EC.20 | Phlogopite | KMg3(AlSi3O10)(OH)2 |
| 9.EC.20 | Yangzhumingite | KMg2.5(Si4O10)F2 |
| 9.EC.20 | Orlovite | KLi2Ti(Si4O10)OF |
| 9.EC.20 | Tetraferriannite | KFe2+3(Si3Fe3+)O10(OH)2 |
| 9.EC.20 | Shirokshinite | K(NaMg2)(Si4O10)F2 |
| 9.EC.20 | Trilithionite | K(Li1.5Al1.5)(AlSi3O10)(F,OH)2 |
| 9.EC.20 | Polylithionite | KLi2Al(Si4O10)(F,OH)2 |
| 9.EC.20 | Shirozulite | KMn2+3(Si3Al)O10(OH)2 |
| 9.EC.20 | Preiswerkite | NaMg2Al(Al2Si2O10)(OH)2 |
| 9.EC.20 | Fluorophlogopite | KMg3(Si3Al)O10F2 |
| 9.EC.20 | Wonesite | (Na,K,◻)(Mg,Fe,Al)6(Si,Al)8O20(OH,F)4 |
| 9.EC.20 | 'UM2004-49-SiO:AlCsFHKLi' | (Cs,K)(Al,Li)2.6((Si,Al)4O10)(F,OH)2 |
| 9.EC.20 | Fluorotetraferriphlogopite | KMg3(Fe3+Si3O10)F2 |
| 9.EC.20 | Annite | KFe2+3(AlSi3O10)(OH)2 |
| 9.EC.20 | Eastonite | KMg2Al(Al2Si2O10)(OH)2 |
| 9.EC.22 | 'Pimelite' | Ni3Si4O10(OH)2 · 4H2O |
| 9.EC.30 | Margarite | CaAl2(Al2Si2O10)(OH)2 |
| 9.EC.35 | Kinoshitalite | (Ba,K)(Mg,Mn2+,Al)3(Al2Si2O10)(OH)2 |
| 9.EC.35 | Ferrokinoshitalite | (Ba,K)(Fe2+,Mg)3(Al2Si2O10)(OH,F)2 |
| 9.EC.35 | Clintonite | CaAlMg2(SiAl3O10)(OH)2 |
| 9.EC.35 | Oxykinoshitalite | (Ba,K)(Mg,Ti,Fe3+,Fe2+)3((Si,Al)4O10)(O,OH,F)2 |
| 9.EC.35 | Fluorokinoshitalite | BaMg3(Al2Si2O10)F2 |
| 9.EC.35 | Bityite | CaLiAl2(AlBeSi2O10)(OH)2 |
| 9.EC.35 | Anandite | (Ba,K)(Fe2+,Mg)3((Si,Al,Fe)4O10)(S,OH)2 |
| 9.EC.40 | Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| 9.EC.40 | Beidellite | (Na,Ca0.5)0.3Al2((Si,Al)4O10)(OH)2 · nH2O |
| 9.EC.40 | Volkonskoite | Ca0.3(Cr,Mg,Fe)2((Si,Al)4O10)(OH)2 · 4H2O |
| 9.EC.40 | Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| 9.EC.40 | Kurumsakite | (Zn,Ni,Cu)8Al8V5+2Si5O35 · 27H2O (?) |
| 9.EC.40 | Yakhontovite | (Ca,Na)0.5(Cu,Fe,Mg)2(Si4O10)(OH)2 · 3H2O |
| 9.EC.45 | Swinefordite | Li(Al,Li,Mg)3((Si,Al)4O10)2(OH,F)4 · nH2O |
| 9.EC.45 | Hectorite | Na0.3(Mg,Li)3(Si4O10)(F,OH)2 |
| 9.EC.45 | Zincsilite | Zn3Si4O10(OH)2 · 4H2O (?) |
| 9.EC.45 | Hanjiangite | Ba2CaV3+Al(H2AlSi3O12)(CO3)2F |
| 9.EC.45 | Spadaite | MgSiO2(OH)2 · H2O (?) |
| 9.EC.45 | Ferrosaponite | Ca0.3(Fe2+,Mg,Fe3+)3((Si,Al)4O10)(OH)2 · 4H2O |
| 9.EC.45 | Stevensite | (Ca,Na)xMg3-x(Si4O10)(OH)2 |
| 9.EC.45 | Saponite | Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O |
| 9.EC.45 | Sauconite | Na0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O |
| 9.EC.50 | Vermiculite | Mg0.7(Mg,Fe,Al)6(Si,Al)8O20(OH)4 · 8H2O |
| 9.EC.52 | 'Tarasovite' | near NaKAl11Si13O40(OH)9 · 3H2O |
| 9.EC.55 | Clinochlore | Mg5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Borocookeite | (LiAl4◻)[BSi3O10](OH)8 |
| 9.EC.55 | Franklinfurnaceite | Ca2Fe3+Mn2+3Mn3+(Zn2Si2O10)(OH)8 |
| 9.EC.55 | Pennantite | Mn2+5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Vakhrushevaite | Mg5Cr(AlSi3O10)(OH)8 |
| 9.EC.55 | Nimite | Ni5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Cookeite | (LiAl4◻)[AlSi3O10](OH)8 |
| 9.EC.55 | Gonyerite | Mn2+5Fe3+(Fe3+Si3O10)(OH)8 |
| 9.EC.55 | Chamosite | Fe2+5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | 'Orthochamosite' | (Fe2+,Mg,Fe3+)5Al(AlSi3O10)(OH,O)8 |
| 9.EC.55 | Baileychlore | Zn5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Sudoite | Mg2Al3(AlSi3O10)(OH)8 |
| 9.EC.55 | Glagolevite | Na(Mg,Al)6(AlSi3O10)(OH,O)8 |
| 9.EC.55 | Donbassite | Al4.33(AlSi3O10)(OH)8 |
| 9.EC.60 | Dozyite | Mg7Al2(Al2Si4O15)(OH)12 |
| 9.EC.60 | Rectorite | (Na,Ca)Al4((Si,Al)8O20)(OH)4 · 2H2O |
| 9.EC.60 | Corrensite | (Mg,Fe)9((Si,Al)8O20)(OH)10 · nH2O |
| 9.EC.60 | Aliettite | Ca0.2Mg6((Si,Al)8O20)(OH)4 · 4H2O |
| 9.EC.60 | Karpinskite | (Ni,Mg)2Si2O5(OH)2 (?) |
| 9.EC.60 | Lunijianlaite | Li0.7Al6.2(AlSi7O20)(OH,O)10 |
| 9.EC.60 | Tosudite | Na0.5(Al,Mg)6((Si,Al)8O18)(OH)12 · 5H2O |
| 9.EC.60 | Hydrobiotite | K(Mg,Fe2+)6((Si,Al)8O20)(OH)4 · nH2O |
| 9.EC.60 | Saliotite | (Li,Na)Al3(AlSi3O10)(OH)5 |
| 9.EC.60 | Kulkeite | Mg8Al(AlSi7O20)(OH)10 |
| 9.EC.60 | Brinrobertsite | Na0.3Al4(Si4O10)2(OH)4 · 3.5 H2O |
| 9.EC.65 | Macaulayite | (Fe,Al)24Si4O43(OH)2 |
| 9.EC.70 | Burckhardtite | Pb2(Fe3+Te6+)[AlSi3O8]O6 |
| 9.EC.75 | Niksergievite | (Ba,Ca)2Al3(AlSi3O10)(CO3)(OH)6 · nH2O |
| 9.EC.75 | Ferrisurite | (Pb,Ca)2.4Fe3+2(Si4O10)(CO3)1.7(OH)3 · nH2O |
| 9.EC.75 | Surite | (Pb,Ca)3(Al,Fe2+,Mg)2((Si,Al)4O10)(CO3)2(OH)2 |
| 9.EC.80 | Kegelite | Pb8Al4(Si8O20)(SO4)2(CO3)4(OH)8 |
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 Willemseite
mindat.org URL:
https://www.mindat.org/min-4293.html
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References for Willemseite
Localities for Willemseite
Showing 19 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.
Australia | |
| Eggleton |
Dominican Republic | |
| Villanova-de-Benavent et al. (2014) |
| M.E. Ciriotti (Steffen Moeckel analysis) | |
France | |
| Berger et al. (2011) +1 other reference |
| Berger et al. (2011) +1 other reference |
| Vale SA |
Germany | |
| Tröger (2012) |
| Gerstenberg (n.d.) |
Greece | |
| Möckel (2000) |
Indonesia | |
| Wei Fu et al. (2010) |
Mexico | |
| - (SGM, 2019) |
New Zealand | |
| Coleman et al. (Lime & Marble Ltd) |
Romania | |
| Hirtopanu et al. (2000) |
South Africa (TL) | |
| Hiemstra et al. (1968) +2 other references |
| Andreoli et al. (1997) +1 other reference |
Switzerland | |
| Ansermet (2012) |
| Ansermet (2012) |
| Ansermet et al. (2025) |
USA | |
| Gobla (2012) |
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Bon Accord Ni deposit, Barberton, Mbombela Local Municipality, Ehlanzeni District Municipality, Mpumalanga, South Africa