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Windhoekite

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About WindhoekiteHide

Formula:
Ca2Fe3+2.67[Si8O20](OH)4 · 10H2O
Colour:
Brown to yellowish brown
Lustre:
Vitreous, Silky
Hardness:
2
Specific Gravity:
2.62
Crystal System:
Monoclinic
Name:
Named for the city of Windhoek, near the type locality.
Visually indistinguishable from tuperssuatsiaite.
Structurally related to tuperssuatsiaite and raite.


Classification of WindhoekiteHide

Approved
Approval Year:
2010
9.EE.20

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

Pronounciation of WindhoekiteHide

Pronounciation:
PlayRecorded byCountry
Debbie WoolfUnited Kingdom

Physical Properties of WindhoekiteHide

Vitreous, Silky
Transparency:
Translucent
Colour:
Brown to yellowish brown
Streak:
Beige
Hardness:
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
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
None observed.
Pleochroism:
Strong
Comments:
Brown to dark brown.

Chemical Properties of WindhoekiteHide

Formula:
Ca2Fe3+2.67[Si8O20](OH)4 · 10H2O
IMA Formula:
Ca2Fe3+3-x[Si8O20](OH)4 · 10H2O

Crystallography of WindhoekiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C1 2/m 1
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

Epitaxial Relationships of WindhoekiteHide

Epitaxial Minerals:
Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O

X-Ray Powder DiffractionHide

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

Type Occurrence of WindhoekiteHide

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:

Synonyms of WindhoekiteHide

Relationship of Windhoekite to other SpeciesHide

Other Members of this group:
Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2OMon. 2/m : B2/m
TuperssuatsiaiteNa2Fe3Si8O20(OH)2 · 4H2OMon. 2/m : B2/m
Unnamed (Na-Ca-Fe-Silicate-Hydrate)NaCa(Fe2+,Al,Mn)5[Si8O19(OH)](OH)7 · 5H2OTric. 1 : P1
YofortieriteMn5Si8O20(OH)2 · 8-9H2OMon. 2/m : B2/m

Common AssociatesHide

Associated Minerals Based on Photo Data:
Neptunite1 photo of Windhoekite associated with Neptunite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.EE.05BementiteMn7Si6O15(OH)8Mon.
9.EE.10BrokenhilliteMn8Si6O15(OH)10Hex. 6mm : P63mc
9.EE.10Pyrosmalite-(Fe)Fe2+8Si6O15(OH,Cl)10Trig. 3m (3 2/m) : P3m1
9.EE.10FriedeliteMn2+8Si6O15(OH,Cl)10Mon. 2/m : B2/m
9.EE.10Pyrosmalite-(Mn)Mn2+8Si6O15(OH,Cl)10Trig.
9.EE.10Mcgillite(Mn,Fe)8Si6O15(OH)8Cl2Mon. 2/m : B2/m
9.EE.15Nelenite(Mn,Fe)16(Si12O30)(OH)14[As3+3O6(OH)3]Mon.
9.EE.15SchalleriteMn2+16As3Si12O36(OH)17Trig. 3m : P3m1
9.EE.20Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2OMon. 2/m : B2/m
9.EE.20TuperssuatsiaiteNa2Fe3Si8O20(OH)2 · 4H2OMon. 2/m : B2/m
9.EE.20YofortieriteMn5Si8O20(OH)2 · 8-9H2OMon. 2/m : B2/m
9.EE.25Falcondoite(Ni,Mg)4Si6O15(OH)2 · 6H2OOrth.
9.EE.25LoughliniteNa2Mg3Si6O16 · 8H2OOrth.
9.EE.25SepioliteMg4(Si6O15)(OH)2 · 6H2OOrth. mmm (2/m 2/m 2/m) : Pnna
9.EE.25Kalifersite(K,Na)5Fe3+7Si20O50(OH)6 · 12H2OTric.
9.EE.30GyroliteNaCa16Si23AlO60(OH)8 · 14H2OTric.
9.EE.30OrlymaniteCa4Mn3Si8O20(OH)6 · 2H2OHex.
9.EE.30TungusiteCa4Fe2Si6O15(OH)6
9.EE.35Reyerite(Na,K)2Ca14(Si,Al)24O58(OH)8 · 6H2OTrig.
9.EE.35Truscottite(Ca,Mn)14Si24O58(OH)8 · 2H2OTrig.
9.EE.40NatrosiliteNa2Si2O5Mon.
9.EE.45MakatiteNa2Si4O8(OH)2 · 4H2OMon. 2/m : P21/b
9.EE.50VarennesiteNa8Mn2Si10O25(OH,Cl)2 · 12H2OOrth.
9.EE.55RaiteNa4Mn2+3Ti0.25Si8O20(OH)2 · 10H2OOrth. 2 2 2 : C2 2 2
9.EE.60IntersiliteNa6Mn2+Ti[Si10O24(OH)](OH)3 · 4H2OMon.
9.EE.65Shafranovskite(Na,K)6(Mn,Fe)3Si9O24 · 6H2OTrig.
9.EE.65ZakharoviteNa4Mn5Si10O24(OH)6 · 6H2OTrig.
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.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.

References for WindhoekiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Chukanov, N.V., Britvin, S.N., Blab, G., Belakovsky, D.I. and Van, K.V. (2011) Windhoekite, IMA 2010-083. CNMNC 2536 Newsletter No. 9, August 2011, page 2537; Mineralogical Magazine, 75, 2535-2540.
Rastsvetaeva, R.K., Aksenov, S. M. and Verin, I. A. (2012): Crystal structure of the NaCa(Fe2+,Al,Mn)5[Si8O19(OH)](OH)7•5H2O mineral: A new representative of the palygorskite group. Crystallography Reports 57, 43-48.
Chukanov, 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. European Journal of Mineralogy, 24, 171-179.

Internet Links for WindhoekiteHide

Localities for WindhoekiteHide

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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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 (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Namibia (TL)
 
  • Khomas Region
    • Windhoek District
      • Aris
Chukanov, N.V., Britvin, S.N., Blab, G., Belakovsky, D.I. and Van, K.V. (2011) Windhoekite, IMA 2010-083. CNMNC 2536 Newsletter No. 9, August 2011, page 2537. Mineralogical Magazine, 75, 2535-2540; Chukanov, 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. European Journal of Mineralogy 24, 171-179; Blass, G. & Tremmel, G. (2014): Neptunit und weitere neue Mineralien aus den Phonolith-Steinbrüchen von Aris, Windhoek. Mineralien-Welt 25 (1), 76-83 (in German).
Mineral and/or Locality  
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