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Posnjakite

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Formula:
Cu4(SO4)(OH)6 · H2O
System:
Monoclinic
Colour:
Sky-blue to dark-blue, ...
Lustre:
Vitreous
Hardness:
2 - 3
Name:
Named in 1967 for Eugene Waldemar Posnjak (1888-1949), U.S. geochemist at the Geophysical Laboratory, Washington, U.S.A., who investigated the system CuO-SO3-H2O.
A copper sulphate hydrate that generally forms at low temperatures (Yoder et al., 2007). Compare also wroewolfeite.

Certain habits are easily confused with the closely related langite.

Classification of Posnjakite

Approved
7.DD.10

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
D : With only medium-sized cations; sheets of edge-sharing octahedra
31.4.1.1

31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
4 : (AB)4(XO4)Zq·xH2O
25.2.8

25 : Sulphates
2 : Sulphates of Cu and Ag
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Type Occurrence of Posnjakite

Year of Discovery:
1967

Physical Properties of Posnjakite

Vitreous
Colour:
Sky-blue to dark-blue, may be slightly greenish-blue.
Streak:
Pale-blue.
Hardness (Mohs):
2 - 3

Crystallography of Posnjakite

Crystal System:
Monoclinic
Class (H-M):
m - Domatic
Space Group:
Pm
Cell Parameters:
a = 10.578(5) Å, b = 6.345(3) Å, c = 7.863(3) Å
β = 117.98(5)°
Ratio:
a:b:c = 1.667 : 1 : 1.239
Unit Cell Volume:
V 466.06 ų
Z:
2
Comment:
Reduced cell is 6.345, 7.863, 9.781 A, 107.247, 90, 89.999°.
X-Ray Powder Diffraction Data:
d-spacingIntensity
7.0 (10)
3.46 (8)
2.70 (7)
2.61 (7)
2.41 (7)
2.015 (7)
1.538 (7)

Optical Data of Posnjakite

Type:
Biaxial (-)
RI values:
nα = 1.625 nβ = 1.680 nγ = 1.706
2V:
Measured: 57° , Calculated: 66°
Max Birefringence:
δ = 0.081
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r < v moderate

Chemical Properties of Posnjakite

Formula:
Cu4(SO4)(OH)6 · H2O
Essential elements:
All elements listed in formula:

Relationship of Posnjakite to other Species

7.DD.05FelsőbányaiteAl4(SO4)(OH)10 · 4H2O
7.DD.10LangiteCu4(SO4)(OH)6 · 2H2O
7.DD.10WroewolfeiteCu4(SO4)(OH)6 · 2H2O
7.DD.15SpangoliteCu6Al(SO4)(OH)12Cl · 3H2O
7.DD.20KtenasiteZn(Cu,Zn)4(SO4)2(OH)6 · 6H2O
7.DD.25ChristeliteCu2Zn3(SO4)2(OH)6 · 4H2O
7.DD.30CampigliaiteMn2+Cu4(SO4)2(OH)6 · 4H2O
7.DD.30DevillineCaCu4(SO4)2(OH)6 · 3H2O
7.DD.30OrthoserpieriteCa(Cu,Zn)4(SO4)2(OH)6 · 3H2O
7.DD.30SerpieriteCa(Cu,Zn)4(SO4)2(OH)6 · 3H2O
7.DD.30NiedermayriteCdCu4(SO4)2(OH)6 · 4H2O
7.DD.30EdwardsiteCu3Cd2(SO4)2(OH)6·4H2O
7.DD.35Carrboydite[(Ni1-xAlx)(OH)2][SO4]x/2 · nH2O
7.DD.35Glaucocerinite(Zn1-xAlx)(OH)2(SO4)x/2 · nH2O
7.DD.35Honessite(Ni1-xFex3+)(OH)2[SO4]x/2 · nH2O
7.DD.35Hydrohonessite(Ni1-xFex3+)(OH)2[SO4]x/2 · nH2O
7.DD.35MotukoreaiteMg6Al3(OH)18[Na(H2O)6][SO4]2 · 6H2O
7.DD.35Mountkeithite[(Mg1-xFex3+)(OH)2][SO4]x/2 · nH2O
7.DD.35ShigaiteMn6Al3(OH)18[Na(H2O)6][SO4]2 · 6H2O
7.DD.35WermlanditeMg7Al2(OH)18[Ca(H2O)6][SO4]2 · 6H2O
7.DD.35WoodwarditeCu1-xAlx(OH)2[SO4]x/2 · nH2O
7.DD.35ZincaluminiteZn6Al6(SO4)2(OH)16 · 5H2O
7.DD.35Hydrowoodwardite(Cu1-xAlx)(OH)2[SO4]x/2 · nH2O
7.DD.35ZincowoodwarditeZn1-xAlx(OH)2[SO4]x/2 · nH2O
7.DD.35NatroglaucoceriniteZn6Al3(OH)18[Na(H2O)6](SO4)2•6H2O
7.DD.35NikischeriteFe62+Al3(OH)18[Na(H2O)6][SO4]2 · 6H2O
7.DD.40Lawsonbauerite(Mn2+,Mg)9Zn4(SO4)2(OH)22 · 8H2O
7.DD.40Torreyite(Mg,Mn2+)72Mn22+Zn4(SO4)2(OH)22 · 8H2O
7.DD.45MooreiteMg92Mn2Zn4(SO4)2(OH)26 · 8H2O
7.DD.50Namuwite(Zn,Cu)4(SO4)(OH)6 · 4H2O
7.DD.55Bechererite(Zn,Cu)6Zn2(SO4,HSiO4)2(OH)12
7.DD.60Ramsbeckite(Cu,Zn)15(SO4)4(OH)22 · 6H2O
7.DD.65VonbezingiteCa6Cu3(SO4)3(OH)12 · 2H2O
7.DD.70RedgilliteCu6(SO4)(OH)10 · H2O
7.DD.75ChalcoalumiteCuAl4(SO4)(OH)12 · 3H2O
7.DD.75Nickelalumite(Ni,Cu)Al4(SO4,(NO3)2)(OH)12 · 3H2O
7.DD.75KyrgyzstaniteZnAl4(SO4)(OH)12·3H2O
7.DD.80Guarinoite(Zn,Co,Ni)6(SO4)(OH,Cl)10 · 5H2O
7.DD.80Schulenbergite(Cu,Zn)7(SO4,CO3)2(OH)10 · 3H2O
7.DD.80Thérèsemagnanite(Co,Zn,Ni)6(SO4)(OH,Cl)10 · 8H2O
7.DD.80UM1992-30-SO:CCuHZn(Zn,Cu)7(SO4,CO3)2(OH)10 · 3H2O
7.DD.85MontetrisaiteCu6(SO4)(OH)10 · 2H2O
25.2.1ChalcocyaniteCuSO4
25.2.2BonattiteCuSO4 · 3H2O
25.2.3ChalcanthiteCuSO4 · 5H2O
25.2.4BoothiteCuSO4 · 7H2O
25.2.5DolerophaniteCu2(SO4)O
25.2.6AntleriteCu3(SO4)(OH)4
25.2.7BrochantiteCu4(SO4)(OH)6
25.2.9LangiteCu4(SO4)(OH)6 · 2H2O
25.2.10WroewolfeiteCu4(SO4)(OH)6 · 2H2O
25.2.11KröhnkiteNa2Cu(SO4)2 · 2H2O
25.2.12NatrochalciteNaCu2(SO4)2(OH) · 2H2O
25.2.13PiypiteK4Cu4O2(SO4)4 · (Na,Cu)Cl
25.2.14FedotoviteK2Cu3(SO4)3O
25.2.15CyanochroiteK2Cu(SO4)2 · 6H2O
25.2.16EuchlorineKNaCu3(SO4)3O
25.2.17DevillineCaCu4(SO4)2(OH)6 · 3H2O
25.2.18LeightoniteK2Ca2Cu(SO4)4 · 2H2O
25.2.19ChalcoalumiteCuAl4(SO4)(OH)12 · 3H2O
25.2.20CyanotrichiteCu4Al2(SO4)(OH)12 · 2H2O
25.2.21WoodwarditeCu1-xAlx(OH)2[SO4]x/2 · nH2O
25.2.22CampigliaiteMn2+Cu4(SO4)2(OH)6 · 4H2O
25.2.23GuilditeCuFe3+(SO4)2(OH) · 4H2O
25.2.24RansomiteCuFe2(SO4)4 · 6H2O
25.2.26KlyuchevskiteK3Cu3(Fe3+,Al)(SO4)4O2
25.2.27Poitevinite(Cu,Fe,Zn)SO4 · H2O
25.2.28ArgentojarositeAgFe33+(SO4)2(OH)6

Other Names for Posnjakite

Name in Other Languages:

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.

References for Posnjakite

Reference List:
American Mineralogist (1967): 52: 1582-1583.

Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva: 96: 58-62.

Mellini, M. & Merlino, S. (1979): Zeitschrift für Kristallographie: 149: 249-257.

American Mineralogist (1983): 68: 1251.

Yoder, C. H., Agee, T. M., Ginion, K. E., Hofmann, A. E., Ewanichak, J. E., Schaeffer, C. D., Jr., Carroll, M. J., Schaeffer, R. W. & McCaffrey, P. F. (2007): The relative stabilities of the copper hydroxyl sulphates. Mineralogical Magazine 71, 571-577.

Internet Links for Posnjakite

Localities for Posnjakite

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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