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Na2Ca5(SO4)6 · 3H2O
Crystal System:
Named after the type locality.
Closely related and very similar to bassanite; found as tiny inclusions in gypsum.
Known as a synthetic phase; some of the Na can be replaced by K.

Chemically related to eugsterite, hydroglauberite, antofagastaite, and partially to cesanite.

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Classification of OmongwaiteHide

Approval Year:

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
D : With only large cations

6 : AXO4·xH2O

Chemical Properties of OmongwaiteHide

Na2Ca5(SO4)6 · 3H2O

Crystallography of OmongwaiteHide

Crystal System:
Class (H-M):
2 - Sphenoidal
Space Group:
Cell Parameters:
a = 12.08(3) Å, b = 6.96(1) Å, c = 6.39(2) Å
β = 90.2°
a:b:c = 1.736 : 1 : 0.918
Unit Cell V:
537 ų

X-Ray Powder DiffractionHide

Powder Diffraction Data:
6.028 Å(40)
3.484 Å(29)
3.019 Å(51)
3.014 Å(100)
2.824 Å(34)
2.820 Å(65)
1.853 Å(23)
1.855 Å(24)

Type Occurrence of OmongwaiteHide

Geological Setting of Type Material:
Inclusions in gypsum crystals in recent evaporite.
Associated Minerals at Type Locality:

Synonyms of OmongwaiteHide

Other Language Names for OmongwaiteHide

Related Minerals - Nickel-Strunz GroupingHide

7.CD.Argesite(NH4)7Bi3Cl16Trig. 3m (3 2/m) : R3c
7.CD.Campostriniite(Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2OMon. 2/m : B2/b
7.CD.05MatteucciteNaHSO4 · H2OMon.
7.CD.10MirabiliteNa2SO4 · 10H2OMon. 2/m
7.CD.15Lecontite(NH4,K)NaSO4 · 2H2OOrth. 2 2 2 : P21 21 21
7.CD.20HydroglauberiteNa10Ca3(SO4)8 · 6H2OMon.
7.CD.25EugsteriteNa4Ca(SO4)3 · 2H2OMon.
7.CD.30GörgeyiteK2Ca5(SO4)6 · H2OMon.
7.CD.35Koktaite(NH4)2Ca(SO4)2 · H2OMon.
7.CD.35SyngeniteK2Ca(SO4)2 · H2OMon. 2/m : P21/m
7.CD.40GypsumCaSO4 · 2H2OMon. 2/m
7.CD.45BassaniteCa(SO4) · 0.5H2OMon. 2 : B2
7.CD.50Zircosulfate(Zr,Ti)(SO4)2 · 4H2OOrth.
7.CD.55SchieffelinitePb10Te6+6O20(OH)14(SO4)(H2O)5Orth. mmm (2/m 2/m 2/m) : Cmcm
7.CD.60MontaniteBi2(TeO6) · 2H2O

Related Minerals - Dana Grouping (8th Ed.)Hide · 0.5H2OMon. 2 : B2

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 OmongwaiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Autenrieth, H. (1958) Untersuchungen im Sechs-Komponenten-System K+, Na+, Mg2+, Ca2+, SO42−, Cl−, H2O mit Schlussfolgerungen für die Verarbeitung der Kalisalze. Kali und Steinsalz: 2(6): 181-200.
Autenrieth, H. (1959) Das Sechs-Komponenten-System K+, Na+, Mg2+, Ca2+, SO42−, (Cl−), H2O bei 90 °C und seine Anwendung auf Schlammprobleme der Kalisalzproduktion. Kali und Steinsalz: 2(2): 395-405.
Gudowius, E., Hodenberg, R.v. (1979) “Natriumpolyhalit”, eine dem Bassanit und dem γ-CaSO4 verwandte Phase. Kali und Steinsalz: 7 (12): 501-504. [as "Natriumpolyhalit"]
Reisdorf, K., Abriel, W. (1987) Reaktionen im System CaSO4-H2O und über Na-polyhalite Na2Ca5(SO4)6 (H2O)3. Neues Jahrbuch für Mineralogie Abhandlungen: 157: 35-46. [as "Na-polyhalite"]
Freyer, D., Reck, G., Bremer, M., Voigt, W. (1999) Thermal behaviour and crystal structure of sodium-containing hemihydrates of calcium sulfate. Monatshefte für Chemie: 130: 1179-1193.
Mees, F., Hatert, F., Rowe, R. (2008) Omongwaite, Na2Ca5(SO4)6.3H2O, a new mineral from recent salt lake deposits, Namibia. Mineralogical Magazine: 72: 1209-1220.

Internet Links for OmongwaiteHide

Localities for OmongwaiteHide

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.
  • Upper Austria
    • Gmunden District
      • Hallstatt
Schorn, A., Neubauer, F., Bernroider, M. (2013): Polyhalite microfabrics in an Alpine evaporite mélange: Hallstatt, Eastern Alps. Journal of Structural Geology 46, 57-75.
Namibia (TL)
  • Omaheke Region
    • Aminuis
Mineralogical Magazine 72,1209-1220(2008)
  • Lower Silesian Voivodeship
    • Kłodzko Co.
      • Nowa Ruda
        • Słupiec Mine
Ł. Kruszewski PXRD data
Mineral and/or Locality  
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