Kröhnkite
A valid IMA mineral species - grandfathered
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About Kröhnkite
Formula:
Na2Cu(SO4)2 · 2H2O
Colour:
Blue, greenish-blue; light blue to colourless in transmitted light
Lustre:
Vitreous
Hardness:
2½ - 3
Specific Gravity:
2.90
Crystal System:
Monoclinic
Member of:
Name:
Named in honor of Johann Berthold Christian Kröhnke (10 December 1832, Glückstadt, Schleswig-Holstein, Germany - 14 June 1915, Hamburg, Germany), chemist who was working in Chile and first analyzed the mineral. He later became a German consul to Chile.
Name Encoding
ASCII-7:
Krohnkite
Unique Identifiers
Mindat ID:
2277
Long-form identifier:
mindat:1:1:2277:0
IMA Classification of Kröhnkite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Na2Cu2+(S6+O4)2·2H2O
Classification of Kröhnkite
7.CC.30
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
C : With medium-sized and large cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
C : With medium-sized and large cations
29.3.2.1
29 : HYDRATED ACID AND NORMAL SULFATES
3 : A2B(XO4)2·xH2O
29 : HYDRATED ACID AND NORMAL SULFATES
3 : A2B(XO4)2·xH2O
25.2.11
25 : Sulphates
2 : Sulphates of Cu and Ag
25 : Sulphates
2 : Sulphates of Cu and Ag
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Khk | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Kröhnkite
Vitreous
Transparency:
Transparent
Colour:
Blue, greenish-blue; light blue to colourless in transmitted light
Streak:
White
Hardness:
2½ - 3 on Mohs scale
Cleavage:
Perfect
On {010} perfect; on {1¯01} very imperfect.
On {010} perfect; on {1¯01} very imperfect.
Fracture:
Conchoidal
Density:
2.90 g/cm3 (Measured) 2.913 g/cm3 (Calculated)
Optical Data of Kröhnkite
Type:
Biaxial (-)
RI values:
nα = 1.544 nβ = 1.578 nγ = 1.601
2V:
Measured: 78° , Calculated: 76°
Max. Birefringence:
δ = 0.057
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
weak
Chemistry of Kröhnkite
Mindat Formula:
Na2Cu(SO4)2 · 2H2O
Element Weights:
Crystallography of Kröhnkite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/c
Cell Parameters:
a = 5.807(1) Å, b = 12.656(2) Å, c = 5.517(1) Å
β = 108.32(1)°
β = 108.32(1)°
Ratio:
a:b:c = 0.459 : 1 : 0.436
Unit Cell V:
384.91 ų (Calculated from Unit Cell)
Morphology:
Crystals short prismatic [001]; also octahedral with large {110} and {011} and rather elongated [100]. Prismatic or fibrous aggregates and crusts; massive, granular.
Twinning:
On {101}, common; twins heart-shaped at times.
Comment:
Cell data from Hawthorne and Ferguson (1975).
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.33 Å | (100) |
| 3.278 Å | (90) |
| 2.757 Å | (90) |
| 2.925 Å | (80) |
| 3.715 Å | (60) |
| 4.145 Å | (40) |
| 3.099 Å | (40) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] | |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] |
Type Occurrence of Kröhnkite
Associated Minerals at Type Locality:
Synonyms of Kröhnkite
Other Language Names for Kröhnkite
Relationship of Kröhnkite to other Species
Member of:
Other Members of Brandtite Group:
| Brandtite | Ca2Mn2+(AsO4)2 · 2H2O | Mon. 2/m : P21/b |
| Dobšináite | Ca2Ca(AsO4)2 · 2H2O | Mon. 2/m : P21/b |
| Roselite | Ca2Co(AsO4)2 · 2H2O | Mon. 2/m : P21/b |
| Rruffite | Ca2Cu(AsO4)2 · 2H2O | Mon. 2/m : P21/b |
| Wendwilsonite | Ca2Mg(AsO4)2 · 2H2O | Mon. 2/m : P21/b |
| Zincroselite | Ca2Zn(AsO4)2 · 2H2O | Mon. 2/m : P21/b |
Common Associates
Associations Based on Photo Data:
| 22 photos of Kröhnkite associated with Natrochalcite | NaCu2(SO4)2(OH) · 2H2O |
| 9 photos of Kröhnkite associated with Changoite | Na2Zn(SO4)2 · 4H2O |
| 7 photos of Kröhnkite associated with Salesite | Cu(IO3)(OH) |
| 7 photos of Kröhnkite associated with Caracolite | Na3Pb2(SO4)3Cl |
| 7 photos of Kröhnkite associated with Antlerite | Cu3(SO4)(OH)4 |
| 4 photos of Kröhnkite associated with Atacamite | Cu2(OH)3Cl |
| 3 photos of Kröhnkite associated with Amarantite | Fe3+2(SO4)2O · 7H2O |
| 3 photos of Kröhnkite associated with Antofagastaite | Na2Ca(SO4)2 · 1.5H2O |
| 2 photos of Kröhnkite associated with Metasideronatrite | Na2Fe(SO4)2(OH) · H2O |
| 2 photos of Kröhnkite associated with Brochantite | Cu4(SO4)(OH)6 |
Related Minerals - Strunz-mindat Grouping
| 7.CC. | Cobaltoblödite | Na2Co(SO4)2 · 4H2O |
| 7.CC. | Andychristyite | PbCu2+Te6+O5(H2O) |
| 7.CC. | Ammoniovoltaite | (NH4)2Fe2+5Fe3+3Al(SO4)12(H2O)18 |
| 7.CC.05 | Krausite | KFe(SO4)2 · H2O |
| 7.CC.10 | Tamarugite | NaAl(SO4)2 · 6H2O |
| 7.CC.15 | Mendozite | NaAl(SO4)2 · 11H2O |
| 7.CC.15 | Kalinite | KAl(SO4)2 · 11H2O |
| 7.CC.20 | Alum-(Na) | NaAl(SO4)2 · 12H2O |
| 7.CC.20 | Lonecreekite | (NH4)Fe3+(SO4)2 · 12H2O |
| 7.CC.20 | Alum-(K) | KAl(SO4)2 · 12H2O |
| 7.CC.20 | Tschermigite | (NH4)Al(SO4)2 · 12H2O |
| 7.CC.20 | Lanmuchangite | Tl+Al(SO4)2 · 12H2O |
| 7.CC.25 | Zincovoltaite | K2Zn5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.25 | Voltaite | K2Fe2+5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.25 | Magnesiovoltaite | K2Mg5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.25 | Pertlikite | K2(Fe2+,Mg)2(Mg,Fe3+)4Fe3+2Al(SO4)12 · 18H2O |
| 7.CC.25 | Ammoniomagnesiovoltaite | (NH4)2Mg2+5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.35 | Ferrinatrite | Na3Fe(SO4)3 · 3H2O |
| 7.CC.40 | Goldichite | KFe(SO4)2 · 4H2O |
| 7.CC.45 | Löweite | Na12Mg7(SO4)13 · 15H2O |
| 7.CC.50 | Nickelblödite | Na2Ni(SO4)2 · 4H2O |
| 7.CC.50 | Blödite | Na2Mg(SO4)2 · 4H2O |
| 7.CC.50 | Changoite | Na2Zn(SO4)2 · 4H2O |
| 7.CC.55 | Leonite | K2Mg(SO4)2 · 4H2O |
| 7.CC.55 | Mereiterite | K2Fe(SO4)2 · 4H2O |
| 7.CC.60 | Nickelpicromerite | K2Ni(SO4)2 · 6H2O |
| 7.CC.60 | Nickelboussingaultite | (NH4)2Ni(SO4)2 · 6H2O |
| 7.CC.60 | Katerinopoulosite | (NH4)2Zn(SO4)2 · 6H2O |
| 7.CC.60 | Picromerite | K2Mg(SO4)2 · 6H2O |
| 7.CC.60 | Cyanochroite | K2Cu(SO4)2 · 6H2O |
| 7.CC.60 | Mohrite | (NH4)2Fe(SO4)2 · 6H2O |
| 7.CC.60 | Boussingaultite | (NH4)2Mg(SO4)2 · 6H2O |
| 7.CC.65 | Polyhalite | K2Ca2Mg(SO4)4 · 2H2O |
| 7.CC.70 | Leightonite | K2Ca2Cu(SO4)4 · 2H2O |
| 7.CC.75 | Amarillite | NaFe(SO4)2 · 6H2O |
| 7.CC.80 | Konyaite | Na2Mg(SO4)2 · 5H2O |
| 7.CC.85 | Wattevilleite | Na2Ca(SO4)2 · 4H2O (?) |
| 7.CC.85 | Xocolatlite | Ca2Mn4+2(Te6+O6)2 · H2O |
| 7.CC.90 | Eckhardite | (Ca,Pb)Cu2+Te6+O5(H2O) |
Other Information
Notes:
Water soluble.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Kröhnkite
mindat.org URL:
https://www.mindat.org/min-2277.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Kröhnkite
Reference List:
Palache, C., Warren, C.H. (1908) Kröhnkite, natrochalcite (a new mineral), and other sulphates from Chile. American Journal Of Science, S. 4 Vol. 26. 342-348
Palache, Ch.; Warren, C. H. (1908) Kröhnkit, Natrochalcit (ein neues Mineral) und andere Sulfate aus Chile. Zeitschrift für Kristallographie, 45 (1-6). 529-538 doi:10.1524/zkri.1908.45.1.529p.534
Palache, C. (1939) Kroehnkite and natrochalcite from Chile. American Journal of Science, 237 (7) 447-455 doi:10.2475/ajs.237.7.447
Hawthorne, F. C., Ferguson, R. B. (1975) Refinement of the crystal structure of kröhnkite. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 31 (6) 1753-1755 doi:10.1107/s0567740875006048
Fleck, Michel, Kolitsch, U., Hertweck, B. (2002) Natural and synthetic compounds with kröhnkite-type chains: review and classification. Zeitschrift für Kristallographie, 217 (9). 435-443 doi:10.1524/zkri.217.9.435.22883
Fleck, Michel, Kolitsch, U. (2003) Natural and synthetic compounds with kröhnkite-type chains. An update. Zeitschrift für Kristallographie, 218 (8). 553-567 doi:10.1524/zkri.218.8.553.20689
Kolitsch, Uwe, Fleck, Michel (2005) Second update on compounds with kröhnkite-type chains. Zeitschrift für Kristallographie, 220 (1). 31-41 doi:10.1524/zkri.220.1.31.58894
Kolitsch, Uwe, Fleck, Michel (2006) Third update on compounds with krohnkite-type chains: the crystal structure of wendwilsonite [Ca2Mg(AsO4)22H2O] and the new triclinic structure types of synthetic AgSc(CrO4)22H2O and M2Cu(Cr2O7)22H2O (M = Rb, Cs) European Journal of Mineralogy, 18 (4) 471-482 doi:10.1127/0935-1221/2006/0018-0471
Majzlan, Juraj, Zittlau, Arne H., Grevel, Klaus-Dieter, Schliesser, Jacob, Woodfield, Brian F., Dachs, Edgar, Števko, Martin, Chovan, Martin, Plášil, Jakub, Sejkora, Jiří, Milovská, Stanislava (2015) Thermodynamic Properties and Phase Equilibria of the Secondary Copper Minerals Libethenite, Olivenite, Pseudomalachite, Kröhnkite, Cyanochroite, and Devilline. The Canadian Mineralogist, 53 (5) 937-960 doi:10.3749/canmin.1400066
Marinova, Delyana, Wildner, Manfred, Bancheva, Tsvetelina, Stoyanova, Radostina, Georgiev, Mitko, Stoilova, Donka G. (2018) Synthesis, structure and properties of blödite-type solid solutions, Na2Co1−xCux(SO4)2·4H2O (0 < x ≤ 0.18), and crystal structure of synthetic kröhnkite, Na2Cu(SO4)2·2H2O. Physics and Chemistry of Minerals, 45 (8) 801-817 doi:10.1007/s00269-018-0963-0
Weil, Matthias, Kolitsch, Uwe (2021) (NH4)Mg(HSO4)(SO4)(H2O)2 and NaSc(CrO4)2(H2O)2, two crystal structures comprising kröhnkite-type chains, and the temperature-induced phase transition (NH4)Mg(HSO4)(SO4)(H2O)2 <-> (NH4)MgH(SO4)2(H2O)2. Acta Crystallographica Section C Structural Chemistry, 77 (3). 144-151 doi:10.1107/s2053229621001650[with updated overview on compounds with kröhnkite-type chains]
Localities for Kröhnkite
Showing 41 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and 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).
All localities listed without proper references should be considered as questionable.
Argentina | |
| Sureda (1978) |
Australia | |
| Birch et al. (1997) |
| Harris et al. (2003) |
| Simpson Mineral Collection of the ... +1 other reference |
Austria | |
| 50. +1 other reference |
Chile | |
| e-rocks.com (2022) |
| SEM-EDS by Igor V. Pekov |
| samples analysed by Dr. Tony Kampf | |
| [www.ontariominerals.com] |
| M.Dini & A.Molina collection | |
| Samples analysed by Dr. Jochen Schlüter (Hamburg University) +1 other reference | |
| Palache et al. (1908) +5 other references |
| Palache et al. (1951) |
| British Natural History Museum online ... | |
| Palache et al. (1951) | |
| CD with abstracts +1 other reference |
| Saric (1978) |
| Teck Resources Limited |
China | |
| Yingxia Xu et al. (2008) |
France | |
| Favreau et al. (2024) |
| Favreau et al. (2024) | |
Greece | |
| Rieck et al. (2018) |
| |
| Rieck (n.d.) | |
Hungary | |
| Mecsek-Oko |
| Koch (1985) |
Iceland | |
| Balić-Žunić et al. (2016) |
| Balić-Žunić et al. (2024) | |
Italy | |
| Balassone et al. (2019) |
| Pellino et al. (2025) | |
| Quagliarella (1966) |
Poland | |
| Łukasz Kruszewski PXRD & EPMA data (2019) |
| Cu +2 other references |
Romania | |
| Onac +4 other references |
Spain | |
| Calvo Rebollar et al. (2022) |
UK | |
| Golley et al. (1995) |
USA | |
| Luetcke (n.d.) |
| Schaller (1903) +3 other references |
| Committee et al. (1989) | |
| Plášil et al. (2013) |
| Dietrich (1990) |
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Chuquicamata Mine, Chuquicamata District, Calama, El Loa Province, Antofagasta, Chile