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(NH4)2Fe33+(SO4)4(OH)3 · 3H2O
Named for Mrs. Claire Martini, wife of Dr. J. C. J. Martini who first described mineral.
Very slowly soluble in water. Chemically related to Unnamed (Fe analogue of huizingite-(Al)), the second both basic and hydrated NH4-Fe sulphate mineral after clairite. Compare also, e.g., carlsonite, lonecreekite; mohrite.

Classification of Clairite

Approval Year:

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
F : With large and medium-sized cations

10 : Miscellaneous

25 : Sulphates
11 : Sulphates of Fe and other metals

Physical Properties of Clairite

Diaphaneity (Transparency):
Transparent, Translucent
2.31 g/cm3 (Measured)    2.32 g/cm3 (Calculated)

Optical Data of Clairite

RI values:
nα = 1.595 nγ = 1.607
Max Birefringence:
δ = 0.012
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
r > v or r < v
X= pale yellow
Z'= dark yellow

Chemical Properties of Clairite

IMA Formula:
(NH4)2Fe33+(SO4)4(OH)3 · 3H2O
Elements listed in formula:

Crystallography of Clairite

Crystal System:
Cell Parameters:
a = 9.36 Å, b = 9.15 Å, c = 52.61 Å
α = 88.15°, β = 90°, γ = 118.36°
a:b:c = 1.023 : 1 : 5.75
Unit Cell Volume:
V 3,962.29 ų (Calculated from Unit Cell)
Powdery aggregates of pseudo-hexagonal plates.
1 or 1
X-Ray Powder Diffraction Data:
17.5 (100)
8.78 (100)
8.23 (20)
4.743 (15)
3.424 (20)
3.279 (25)
3.041 (20)

Type Occurrence of Clairite

Place of Conservation of Type Material:
Museum of the Geological Survey of South Africa (now the Council for Geoscience), Pretoria, South Africa
Geological Setting of Type Material:
Alteration of pyrite and decaying organic material (Hyrex excreta).
Empirical Formula:
(NH4)2Fe33+(SO4)4(OH)3 · 3H2O

Relationship of Clairite to other Species

7.DF.05UklonskoviteNaMg(SO4)F · 2H2O
7.DF.10KainiteKMg(SO4)Cl · 3H2O
7.DF.15NatrochalciteNaCu2(SO4)2(OH) · H2O
7.DF.20MetasideronatriteNa2Fe3+(SO4)2(OH) · H2O
7.DF.20SideronatriteNa2Fe3+(SO4)2(OH) · 3H2O
7.DF.25DespujolsiteCa3Mn4+(SO4)2(OH)6 · 3H2O
7.DF.25FleischeritePb3Ge(SO4)2(OH)6 · 3H2O
7.DF.25SchaurteiteCa3Ge4+(SO4)2(OH)6 · 3H2O
7.DF.25MallestigitePb3Sb(SO4)(AsO4)(OH)6 · 3H2O
7.DF.30Slavíkite(H3O)31+Mg6Fe15(SO4)21(OH)18 · 98H2O
7.DF.35MetavoltineK2Na6Fe2+Fe63+O2(SO4)12 · 18H2O
7.DF.40LannoniteHCa4Mg2Al4(SO4)8F9 · 32H2O
7.DF.40VlodavetsiteCa2Al(SO4)2F2Cl · 4H2O
7.DF.45PeretaiteCaSb43+O4(SO4)2(OH)2 · 2H2O
7.DF.50GordaiteNaZn4(SO4)(OH)6Cl · 6H2O
7.DF.60ArzrunitePb2Cu4SO4(OH)4Cl6 · 2H2O
7.DF.65ElyiteCuPb4(SO4)O2(OH)4 · H2O
7.DF.70YecoraiteFe33+Bi5O9(Te4+O3)(Te6+O4)2 · 9H2O
7.DF.75RiomarinaiteBiSO4(OH) · H2O
7.DF.80DukeiteBi243+Cr86+O57(OH)6 · 3H2O
7.DF.85XocolatliteCa2Mn24+Te26+O12 · H2O
25.11.2SideronatriteNa2Fe3+(SO4)2(OH) · 3H2O
25.11.3MetasideronatriteNa2Fe3+(SO4)2(OH) · H2O
25.11.4FerrinatriteNa3Fe3+(SO4)3 · 3H2O
25.11.5AmarilliteNaFe3+(SO4)2 · 6H2O
25.11.7KrausiteKFe3+(SO4)2 · H2O
25.11.8GoldichiteKFe3+(SO4)2 · 4H2O
25.11.10VoltaiteK2Fe52+Fe33+Al(SO4)12 · 18H2O
25.11.11UngemachiteK3Na8Fe3+(SO4)6(NO3)2 · 6H2O
25.11.12MetavoltineK2Na6Fe2+Fe63+O2(SO4)12 · 18H2O
25.11.16Mohrite(NH4)2Fe2+(SO4)2 · 6H2O
25.11.17LonecreekiteNH4Fe3+(SO4)2 · 12H2O
25.11.19BotryogenMgFe3+(SO4)2(OH) · 7H2O
25.11.21Slavíkite(H3O)31+Mg6Fe15(SO4)21(OH)18 · 98H2O
25.11.23SturmaniteCa6Fe23+(SO4)2.5[B(OH)4](OH)12 · 25H2O
25.11.25Aluminocopiapite(Al,Mg)Fe43+(SO4)6(OH,O)2 · 20H2O
25.11.26HalotrichiteFe2+Al2(SO4)4 · 22H2O
25.11.27Idrizite(Mg,Fe)(Al,Fe)2(SO4)3(OH)2 · 15H2O or near
25.11.28LishizheniteZnFe23+(SO4)4 · 14H2O
25.11.29ZincovoltaiteK2Zn5Fe33+Al(SO4)12 · 18H2O

Other Names for Clairite

Name in Other Languages:

Other Information

Other Information:
Very slowly soluble in water.
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 Clairite

Reference List:
Martini, J. E. J. (1984): Lonecreekite, sabieite, and clairite, new secondary ammonium ferric-iron sulfates from Lone Creek Fall cave, near Sabie, eastern Transvaal. Annals of the Geological Survey (South Africa), 17, 29-34.

American Mineralogist: 71: 229.

Daltry, V.D.C. (1997) Mineralogy of South Africa: Type-Mineral Species and Type-Mineral Names. Council For Geoscience, Geological Survey of South Africa, Handbook 15.

Internet Links for Clairite URL:
Please feel free to link to this page.

Localities for Clairite

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.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
  • Baden-Württemberg
    • Black Forest
      • Wolfach
        • Oberwolfach
          • Rankach valley
Walenta, K. (1992): Die Mineralien des Schwarzwaldes. Chr. Weise Verlag, München, 336 pp. (in German); WALENTA, K. (1997): Neue Mineralfunde von der Grube Clara 7. Folge. - Lapis 22 (11), 37-47.
  • North Rhine-Westphalia
    • Aachen
      • Alsdorf
Witzke, T., de Wit, F., Kolitsch, U. and Blaß, G. (2015): Mineralogy of the Burning Anna I Coal Mine Dump, Alsdorf, Germany. Chapter 7, pp. 203-240, in: Stracher, G. B., Prakash, A. and Sokol, E. V.: Coal and Peat Fires: A Global Perspective, Volume 3: Case Studies - Coal Fires, Elsevier, 786 pp.
  • Baranya Co.
    • Mecsek Mts
      • Komló
Mineral Species of Hungary, 2005
      • Pécs
Szakáll, S. & Kristály, F. (2008): Ammonium sulphates from burning coal dumps at Komló and Pécs-Vasas, Mecsek Mts., South Hungary. Mineralogia, Special Papers, Vol. 32 (2nd Central-European Mineralogical Conference 2008 (CEMC)), 154.
  • Upper Silesia (Śląskie)
    • Upper Silesian Coal Basin
      • Katowice area
Parafiniuk, J. and Kruszewski, Ł. (2009): Ammonium minerals from burning coal-dumps of the Upper Silesian Coal Basin (Poland). Geol. Quart., 53, 341-356. (esp. p. 347)]
South Africa (TL)
  • Mpumalanga Province
    • Ehlanzeni District
      • Pilgrim's Rest
        • Sabie
          • Lone Creek Falls
Ann.Geol.Survey S.Africa,(1983) 17, 29-34; Daltry, V.D.C., (1997) Mineralogy of South Africa: Type-Mineral Species and Type-Mineral Names, Council For Geoscience, Geological Survey of South Africa, Handbook 15.
  • Ohio
    • Huron Co.
      • Huron River
Dr Pete Richards
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