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Posnjakite

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Eugene W. Posnjak
Formula:
Cu4(SO4)(OH)6 · H2O
Colour:
Sky-blue to dark-blue, may be slightly greenish-blue.
Lustre:
Vitreous
Hardness:
2 - 3
Specific Gravity:
3.32
Crystal System:
Monoclinic
Name:
Named in 1967 by A. I. Komkov and E. I. Nefedov in honour of Eugene Waldemar Posnjak (23 June 1888, Moscow, Russia - 31 July 1949, Santa Barbara, California), 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

Physical Properties of Posnjakite

Vitreous
Colour:
Sky-blue to dark-blue, may be slightly greenish-blue.
Streak:
Pale-blue.
Hardness:
2 - 3 on Mohs scale
Density:
3.32 g/cm3 (Measured)    3.35 g/cm3 (Calculated)

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
Pleochroism:
Visible
Comments:
X = bluish to colorless, Y = blue to dark blue, Z = greenish blue to blue

Chemical Properties of Posnjakite

Formula:
Cu4(SO4)(OH)6 · H2O
IMA Formula:
Cu4SO4(OH)6 · H2O

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 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

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)

Type Occurrence of Posnjakite

Synonyms of Posnjakite

Other Language Names for Posnjakite

Common Associates

Associated Minerals Based on Photo Data:
Langite27 photos of Posnjakite associated with Langite on mindat.org.
Malachite17 photos of Posnjakite associated with Malachite on mindat.org.
Devilline16 photos of Posnjakite associated with Devilline on mindat.org.
Brochantite12 photos of Posnjakite associated with Brochantite on mindat.org.
Linarite8 photos of Posnjakite associated with Linarite on mindat.org.
Cerussite6 photos of Posnjakite associated with Cerussite on mindat.org.
Schulenbergite4 photos of Posnjakite associated with Schulenbergite on mindat.org.
Chalcopyrite3 photos of Posnjakite associated with Chalcopyrite on mindat.org.
Serpierite3 photos of Posnjakite associated with Serpierite on mindat.org.
Ramsbeckite3 photos of Posnjakite associated with Ramsbeckite on mindat.org.

Related Minerals - Nickel-Strunz Grouping

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-xFe3+x)(OH)2[SO4]x/2 · nH2O
7.DD.35Hydrohonessite(Ni1-xFe3+x)(OH)2[SO4]x/2 · nH2O
7.DD.35MotukoreaiteMg6Al3(OH)18[Na(H2O)6][SO4]2 · 6H2O
7.DD.35Mountkeithite[(Mg1-xFe3+x)(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.35NikischeriteFe2+6Al3(OH)18[Na(H2O)6][SO4]2 · 6H2O
7.DD.40Lawsonbauerite(Mn2+,Mg)9Zn4(SO4)2(OH)22 · 8H2O
7.DD.40Torreyite(Mg,Mn2+)72Mn2+2Zn4(SO4)2(OH)22 · 8H2O
7.DD.45MooreiteMg92Mn2Zn4(SO4)2(OH)26 · 8H2O
7.DD.50NamuwiteZn4(SO4)(OH)6 · 4H2O
7.DD.55BechereriteZn7Cu(OH)13[(SiO(OH)3(SO4)]
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.80GuarinoiteZn6(SO4)(OH)10 · 5H2O
7.DD.80Schulenbergite(Cu,Zn)7(SO4)2(OH)10 · 3H2O
7.DD.80ThérèsemagnaniteNaCo4(SO4)(OH)6Cl·6H2O
7.DD.80UM1992-30-SO:CCuHZn(Zn,Cu)7(SO4,CO3)2(OH)10 · 3H2O
7.DD.85MontetrisaiteCu6(SO4)(OH)10 · 2H2O

Related Minerals - Hey's Chemical Index of Minerals Grouping

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
25.2.28ArgentojarositeAgFe3+3(SO4)2(OH)6

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:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Komkov, A.I., Nefedov, E.I. (1967) Posnjakite, a new mineral. Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva: 96: 1: 58-62.
Fleischer, M. (1967) New mineral names. American Mineralogist: 52: 1579-1589.
Mellini, M., Merlino, S. (1979) Posnjakite: 2∞[Cu4(OH)6(H2O)O] octahedral sheets in its structure. Zeitschrift für Kristallographie: 149: 249-257.
Iakhontova, L.K. (1981) New data on posnjakite, serpierite and woodwardite. Doklady Akademii Nauk SSSR: 256: 1221-1225.
Ridkosil, T., Povondra, P. (1982) The relation between posnjakite and langite. Neues Jahrbuch für Mineralogie Monatshefte: 16-28.
Dunn, P.J., Fleischer, M. Chao, G.Y., Cabri, L.J., and Mandarino, J.A. (1983) New mineral names. American Mineralogist: 68: 1248-1252.
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

mindat.org URL:
https://www.mindat.org/min-3265.html
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Specimens:
The following Posnjakite specimens are currently listed for sale on minfind.com.

Localities for Posnjakite

Mineral and/or Locality  
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