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Windhoekite

A valid IMA mineral species
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05700400017272472035035.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
00031240017272472048409.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
01869100017671061191122.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
05700400017272472035035.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
00031240017272472048409.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
05658540017642424692030.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
09734620017272472048257.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
02267860017272472056122.jpg
Windhoekite

Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
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About WindhoekiteHide

08118520017272003997699.jpg
Windhoek District near Aris

Windhoek Rural, Khomas Region, Namibia
Formula:
Fe3+(Fe3+1.67◻0.33)Ca2◻2Si8O20(OH)2(H2O)4(OH)2 · 6H2O
Colour:
Brown to yellowish brown
Lustre:
Vitreous, Silky
Hardness:
2
Specific Gravity:
2.62
Crystal System:
Monoclinic
Name:
Named for the type locality at the Aris intrusion in the Windhoek district, Namibia.
Visually indistinguishable from tuperssuatsiaite.
Structurally related to tuperssuatsiaite and raite.


Unique IdentifiersHide

Mindat ID:
41574
Long-form identifier:
mindat:1:1:41574:9

IMA Classification of WindhoekiteHide

IMA status:
Approved
IMA Formula:
Ca2Fe3+2.67(Si8O20)(OH)4·10H2O
Approval year:
2010

Classification of WindhoekiteHide

Strunz-mindat (2026):
9.EE.20

9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands

Mineral SymbolsHide

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.

SymbolSourceReference for Standard
WhkIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43
WhkWarr (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

Pronunciation of WindhoekiteHide

Pronunciation:
PlayRecorded byCountry
Debbie WoolfUnited Kingdom

Physical Properties of WindhoekiteHide

Lustre:
Vitreous, Silky
Transparency:
Translucent
Colour:
Brown to yellowish brown
Streak:
Beige
Hardness:
2 on Mohs scale
Tenacity:
Sectile
Cleavage:
Perfect
on {100}
Density:
2.62(2) g/cm3 (Measured)    2.630 g/cm3 (Calculated)

Optical Data of WindhoekiteHide

Type:
Biaxial (-)
RI values:
nα = 1.610(3) nβ = 1.662(3) nγ = 1.671(3)
2V:
Measured: 50° (10), Calculated: 44°
Max. Birefringence:
δ = 0.061
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.

Surface Relief:
High (positive)
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.
Dispersion:
None observed.
Pleochroism:
Strong
Comments:
Brown to dark brown.

Chemistry of WindhoekiteHide

Mindat Formula:
Fe3+(Fe3+1.67◻0.33)Ca2◻2Si8O20(OH)2(H2O)4(OH)2 · 6H2O
Element Weights:
Element% weight
O53.221 %
Si21.982 %
Fe14.588 %
Ca7.842 %
H2.367 %

Calculated from ideal end-member formula.
O
Si
Fe
Ca
H
Elements listed:
Ca, Fe, H, O, Si - search for minerals with similar chemistry

Crystallography of WindhoekiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C12/m1
Cell Parameters:
a = 14.319(5) Å, b = 17.825(4) Å, c = 5.242(1) Å
β = 103.5(2)°
Ratio:
a:b:c = 0.803 : 1 : 0.294
Unit Cell V:
1301 ų
Z:
2

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0018919WindhoekiteChukanov N V, Britvin S N, Blass G, Belakovskiy D I, Van K V (2012) Windhoekite, Ca2Fe3+3-x(Si8O20)(OH)4*10H2O, a new palygorskite-group mineral from the Aris phonolite, Namibia crystal structure. The structure is missing two oxygens, and the OH positions were not given. European Journal of Mineralogy 24 171-1792012Aris phonolite, Namibia0293
CIF Raw Data - click here to close

Epitaxial Relationships of WindhoekiteHide

Epitaxial Minerals:
'Palygorskite'◻Al2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2O

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
11.04 Å(100)
4.432 Å(10)
4.134 Å(6)
3.749 Å(4)
3.486 Å(11)
2.636 Å(8)
2.550 Å(4)
2.507 Å(6)

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 4b: Highly evolved igneous rocks>3.0
35 : Ultra-alkali and agpaitic igneous rocks

Type Occurrence of WindhoekiteHide

Type Locality:
ⓘ Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia
General Appearance of Type Material:
Isolated long-prismatic crystals up to 0.15 mm across and 4 mm in length, and their radial aggregates up to 5 mm in size.
Place of Conservation of Type Material:
Type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, registration number 4018/1.
Geological Setting of Type Material:
Hydrothermal mineral in miarolitic cavities of phonolite.
Associated Minerals at Type Locality:
AegirineArisite-(Ce)Arisite-(La)Fluorapophyllite-(K)Microcline
Palygorskite

Synonyms of WindhoekiteHide

Other Language Names for WindhoekiteHide

Relationship of Windhoekite to other SpeciesHide

Member of:
Palygorskite Group
Other Members of Palygorskite Group:
IkorskyiteKMn3+(Si4O10) · 3H2OMon. 2/m : P21/b
Palygorskite◻Al2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2OMon. 2/m : B2/m
RaiteMn2+Mn2+2Na2(◻1.75Ti0.25)Si8O20(OH)2(H2O)4 · Na(H2O)6Orth. 222 : C222
TuperssuatsiaiteFe3+Fe3+2(Na◻)◻2Si8O20(OH)2(H2O)4 · 2H2OMon. 2/m : B2/m
'Unnamed (Na-Ca-Fe-Silicate-Hydrate)'NaCa(Fe2+,Al,Mn)5[Si8O19(OH)](OH)7 · 5H2OTric. 1 : P1
Windmountainite◻Fe3+2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2OMon. 2/m : B2/m
YofortieriteMn2+Mn2+2Mn2+2◻2Si8O20(OH)2(H2O)4 · 4H2OMon. 2/m : B2/m

Common AssociatesHide

Associations Based on Photo Data:
1 photo of Windhoekite associated with NeptuniteKNa2Li(Fe2+)2Ti2[Si4O12]2

Related Minerals - Strunz-mindat GroupingHide

9.EE.CairncrossiteSr2Ca7-xNa2x(Si4O10)4(OH)2(H2O)15-xTric. 1 : P1
9.EE.05BementiteMn7Si6O15(OH)8Mon.
9.EE.07InnsbruckiteMn33(Si2O5)14(OH)38Mon. m : Bm
9.EE.10'Brokenhillite'Mn8Si6O15(OH)10Hex. 6mm : P63mc
9.EE.10Mcgillite(Mn,Fe)8Si6O15(OH)8Cl2Mon. 2/m : B2/m
9.EE.10FriedeliteMn2+8Si6O15(OH,Cl)10Mon. 2/m : B2/m
9.EE.10Pyrosmalite-(Mn)Mn2+8Si6O15(OH,Cl)10Trig. 3m(32/m) : P3m1
9.EE.10Pyrosmalite-(Fe)Fe2+8Si6O15(OH,Cl)10Trig. 3m(32/m) : P3m1
9.EE.15NeleniteMn2+16As3+3Si12O36(OH)17Trig. 3m(32/m) : R3m
9.EE.15SchalleriteMn2+16As3Si12O36(OH)17Trig. 3m : P3m1
9.EE.20Palygorskite◻Al2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2OMon. 2/m : B2/m
9.EE.20YofortieriteMn2+Mn2+2Mn2+2◻2Si8O20(OH)2(H2O)4 · 4H2OMon. 2/m : B2/m
9.EE.20Windmountainite◻Fe3+2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2OMon. 2/m : B2/m
9.EE.20IkorskyiteKMn3+(Si4O10) · 3H2OMon. 2/m : P21/b
9.EE.20TuperssuatsiaiteFe3+Fe3+2(Na◻)◻2Si8O20(OH)2(H2O)4 · 2H2OMon. 2/m : B2/m
9.EE.20'Unnamed (Na-Ca-Fe-Silicate-Hydrate)'NaCa(Fe2+,Al,Mn)5[Si8O19(OH)](OH)7 · 5H2OTric. 1 : P1
9.EE.25SepioliteMg4(Si6O15)(OH)2 · 6H2OOrth. mmm(2/m2/m2/m) : Pnna
9.EE.25LoughliniteNa2Mg3Si6O16 · 8H2OOrth. mmm(2/m2/m2/m)
9.EE.25Falcondoite(Ni,Mg)4Si6O15(OH)2 · 6H2OOrth.
9.EE.25Kalifersite(K,Na)5Fe3+7Si20O50(OH)6 · 12H2OTric. 1 : P1
9.EE.30OrlymaniteCa4Mn3Si8O20(OH)6 · 2H2OHex.
9.EE.30TungusiteCa4Fe2Si6O15(OH)6Tric. 1 : P1
9.EE.30GyroliteNaCa16Si23AlO60(OH)8 · 14H2OTric. 1 : P1
9.EE.35Reyerite(Na,K)2Ca14(Si,Al)24O58(OH)8 · 6H2OTrig. 3 : P3
9.EE.35KodamaiteNa3(Ca5Na)Si16O36(OH)4F2 · (14-x)H2OTric. 1 : P1
9.EE.35Truscottite(Ca,Mn)14Si24O58(OH)8 · 2H2OTrig.
9.EE.40NatrosiliteNa2Si2O5Mon. 2/m : P21/b
9.EE.45MakatiteNa2Si4O8(OH)2 · 4H2OMon. 2/m : P21/b
9.EE.50VarennesiteNa8Mn2Si10O25(OH,Cl)2 · 12H2OOrth. mmm(2/m2/m2/m) : Cmcm
9.EE.55RaiteMn2+Mn2+2Na2(◻1.75Ti0.25)Si8O20(OH)2(H2O)4 · Na(H2O)6Orth. 222 : C222
9.EE.60IntersiliteNa6Mn2+Ti[Si10O24(OH)](OH)3 · 4H2OMon.
9.EE.65ZakharoviteNa4Mn5Si10O24(OH)6 · 6H2OTrig. 3m
9.EE.65ShafranovskiteNa3K2(Mn,Fe,Na)4[Si9(O,OH)27](OH)2 · nH2OTrig. 3m : P31c
9.EE.70ZeophylliteCa13Si10O28(OH)2F8 · 6H2OTrig. 3 : R3
9.EE.75Minehillite(K,Na)2-3Ca28Zn4Al4Si40O112(OH)16Hex.
9.EE.80Fedorite(Na,K)2-3(Ca4Na3)Si16O38(OH,F)2 · 3.5H2OTric. 1 : P1
9.EE.80Martinite(Na,◻,Ca)12Ca4(Si,S,B)14B2O38(OH,Cl)2F2 · 4H2OTric. 1 : P1
9.EE.80EllingseniteNa5Ca6Si18O38(OH)13 · 6H2OTric. 1 : P1
9.EE.85Lalondeite(Na,Ca)6(Ca,Na)3Si16O38(F,OH)2 · 3H2OTric. 1 : P1

Other InformationHide

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 WindhoekiteHide

References for WindhoekiteHide

Localities for WindhoekiteHide

Showing 2 localities.

This 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.
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Locality ListHide

- 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Namibia (TL)
 
  • Khomas Region
    • Windhoek Rural
      • Aris
Williams et al. (2011) +2 other references
Ukraine
 
  • Crimea
    • Bakhchysarai
      • Trudolyubovka
Kasatkin (2019)
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