Kainite
A valid IMA mineral species - grandfathered
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About Kainite
Formula:
KMg(SO4)Cl · 3H2O
Borisov et al. (2022) propose the formula KMg(SO4)Cl⋅2.75H2O.
Colour:
Colourless; yellow, brownish, greyish-green, red, violet, blue; colourless in transmitted light.
Lustre:
Vitreous
Hardness:
2½ - 3
Specific Gravity:
2.15
Crystal System:
Monoclinic
Name:
From Greek καιυος = "recent," in allusion to its recent formation as a secondary mineral.
This page provides mineralogical data about Kainite.
Unique Identifiers
Mindat ID:
2132
Long-form identifier:
mindat:1:1:2132:2
Similar Names
| Cahnite | A valid IMA mineral species - grandfathered | Ca2[B(OH)4](AsO4) |
| Conite (of Macculloch) | A synonym of Quartz | |
| Gahnite | A valid IMA mineral species - grandfathered | ZnAl2O4 |
| Gahnite (of Lobo da Silveira) | A synonym of Vesuvianite | |
| Guanite | A synonym of Struvite | |
| Hainite-(Y) | A valid IMA mineral species - grandfathered | Na2Ca4(Y,REE)Ti(Si2O7)2OF3 |
| Kalinite | A valid IMA mineral species - grandfathered | KAl(SO4)2 · 11H2O |
| Kaneite | MnAs | |
| Kanoite | A valid IMA mineral species | Mn2+MgSi2O6 |
| Kenyte | A rock subtype | |
| Khinite | A valid IMA mineral species | Pb2+Cu32+[Te6+O6](OH)2 |
| Kinoite | A valid IMA mineral species | Ca2Cu2(H2O)2[Si3O10] |
| Konit | A synonym of 'Mg-rich Dolomite' | |
| Kyanite | A valid IMA mineral species - grandfathered | Al2(SiO4)O |
| Kühnite | A synonym of Berzeliite | |
| Painite | A valid IMA mineral species - grandfathered | CaZrAl9(BO3)O15 |
IMA Classification of Kainite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
KMg(S6+O4)Cl·2.75H2O
First published:
1865
Classification of Kainite
7.DF.10
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
F : With large and medium-sized cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
F : With large and medium-sized cations
31.7.1.1
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
7 : (AB)2(XO4)Zq·xH2O
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
7 : (AB)2(XO4)Zq·xH2O
26.14
26 : Sulphates with Halide
26 : Sulphates with Halide
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 |
|---|---|---|
| Kai | 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 Kainite
Vitreous
Transparency:
Transparent
Colour:
Colourless; yellow, brownish, greyish-green, red, violet, blue; colourless in transmitted light.
Comment:
Tints due to included matter. Violet-coloured material is decolourized at 150°C. H2S identified in blue material (Leonhardt and Kühn).
Streak:
White
Hardness:
2½ - 3 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
{001}, perfect.
{001}, perfect.
Fracture:
Splintery
Density:
2.15 g/cm3 (Measured) 2.24 g/cm3 (Calculated)
Optical Data of Kainite
Type:
Biaxial (-)
RI values:
nα = 1.494 nβ = 1.505 nγ = 1.516
2V:
Measured: 90° , Calculated: 88°
Max. Birefringence:
δ = 0.022
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
Dispersion:
weak
Optical Extinction:
X = a; Y = b; Z ∧ c = 13°.
Pleochroism:
Visible
Comments:
X = Violet
Y = Blue
Z = Yellowish
Observed on blue or violet material only.
Y = Blue
Z = Yellowish
Observed on blue or violet material only.
Chemistry of Kainite
Mindat Formula:
KMg(SO4)Cl · 3H2O
Borisov et al. (2022) propose the formula KMg(SO4)Cl⋅2.75H2O.
Borisov et al. (2022) propose the formula KMg(SO4)Cl⋅2.75H2O.
Element Weights:
Crystallography of Kainite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 19.6742(2) Å, b = 16.18240(10) Å, c = 9.49140(10) Å
β = 94.8840(10)°
β = 94.8840(10)°
Ratio:
a:b:c = 1.216 : 1 : 0.587
Unit Cell V:
3010.86 ų
Z:
16
Morphology:
Crystals thick tabular {100} to equidimensional; often exhibiting numerous forms. Occurs as crystalline coatings and clusters in cavities or fissures in which single crystals may reach several centimeters; granular massive.
Comment:
Borisov et al. (2022).
Crystallographic forms of Kainite
Crystal Atlas:
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Kainite no.2 - {001} - Goldschmidt (1913-1926)
Kainite no.4 - {111} - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by
www.smorf.nl.
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0000291 | Kainite | Robinson P D, Fang J H, Ohya Y (1972) The crystal structure of kainite American Mineralogist 57 1325-1332 |  | 1972 | Stassfurt, Germany | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.372 Å | (100) |
| 3.080 Å | (86) |
| 7.771 Å | (83) |
| 8.115 Å | (69) |
| 3.029 Å | (66) |
| 3.048 Å | (42) |
| 4.616 Å | (37) |
Comments:
Calculated, ICDD 25-1237.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 45a : [Sulfates, arsenates, selenates, antimonates] | |
| 45b : [Other oxidized fumarolic minerals] | |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] | |
| 47g : [Halogen-bearing surface weathering minerals] |
Type Occurrence of Kainite
Place of Conservation of Type Material:
No designated type material.
Geological Setting of Type Material:
Potash deposit of oceanic origin.
Synonyms of Kainite
Other Language Names for Kainite
Common Associates
Related Minerals - Strunz-mindat Grouping
| 7.DF. | Siligiite | [Pb(H2O)5(SO4)][Zn9(OH)18] |
| 7.DF. | Alcaparrosaite | K3Ti4+Fe3+(SO4)4O(H2O)2 |
| 7.DF. | Flaggite | Pb4Cu2+4Te6+2(SO4)2O11(OH)2(H2O) |
| 7.DF. | Bairdite | Pb2Cu2+4Te6+2O10(OH)2(SO4) · H2O |
| 7.DF. | Tzeferisite | CaZn8(SO4)2(OH)12Cl2(H2O)9 |
| 7.DF. | Cherokeeite | [Pb2Zn(OH)4](SO4) · H2O |
| 7.DF. | Ammoniomathesiusite | (NH4)5(UO2)4(SO4)4(VO5) · 4H2O |
| 7.DF. | Sigogglinite | [Pb6Zn(OH)8]2(SO4)6 · (H2O)8-x |
| 7.DF.X | Blueridgeite | [Pb8Zn3Cu2+(OH)16](SO4)2(S2O3)2 · 2H2O |
| 7.DF. | Erssonite | Mg7Fe3+2(OH)18[Ca(H2O)6](SO4)2 · 12H2O |
| 7.DF. | Poellmannite | Ca6Al3(OH)18[Na(H2O)6](SO4)2 · 6H2O |
| 7.DF. | Carlsonite | (NH4)5Fe3+3O(SO4)6 · 7H2O |
| 7.DF. | Cuprocherokeeite | [Pb8Zn3Cu2+(OH)16](SO4)4 · 4H2O |
| 7.DF. | Haywoodite | [Pb(H2O)10][Zn12(OH)20(H2O)(SO4)3] |
| 7.DF. | Chromschieffelinite | Pb10Te6+6O20(OH)14(CrO4)(H2O)5 |
| 7.DF.05 | Uklonskovite | NaMg(SO4)F · 2H2O |
| 7.DF.10 | Kaliochalcite | KCu2(SO4)2[(OH)(H2O)] |
| 7.DF.15 | Natrochalcite | NaCu2(SO4)2(OH) · 2H2O |
| 7.DF.17 | Genplesite | Ca3Sn(SO4)2(OH)6 · 3H2O |
| 7.DF.17 | 'Unnamed (Ba-Sb Silicate-Sulphate-Hydroxide-Hydrate)' | Ba3Sb5+[(Si,S)O3(OH)]2(OH,O)6 · 3H2O |
| 7.DF.20 | Sideronatrite | Na2Fe(SO4)2(OH) · 3H2O |
| 7.DF.20 | Metasideronatrite | Na2Fe(SO4)2(OH) · H2O |
| 7.DF.25 | Fleischerite | Pb3Ge(SO4)2(OH)6 · 3H2O |
| 7.DF.25 | Mallestigite | Pb3Sb5+(SO4)(AsO4)(OH)6 · 3H2O |
| 7.DF.25 | Schaurteite | Ca3Ge(SO4)2(OH)6 · 4H2O |
| 7.DF.25 | Despujolsite | Ca3Mn4+(SO4)2(OH)6 · 3H2O |
| 7.DF.30 | Slavíkite | (H3O+)3Mg6Fe15(SO4)21(OH)18 · 98H2O |
| 7.DF.35 | Metavoltine | K2Na6Fe2+Fe3+6O2(SO4)12 · 18H2O |
| 7.DF.40 | Lannonite | Mg2Ca4Al4(SO4)8F8 · 24H2O |
| 7.DF.40 | Vlodavetsite | AlCa2(SO4)2F2Cl · 4H2O |
| 7.DF.45 | Peretaite | Ca(SbO)4(SO4)2(OH)2 · 2H2O |
| 7.DF.50 | Gordaite | NaZn4(SO4)(OH)6Cl · 6H2O |
| 7.DF.50 | Calamaite | Na2TiO(SO4)2 · 2H2O |
| 7.DF.52 | Huizingite-(Al) | [(NH4)9(SO4)2][(Al,Fe3+)3(OH)2(H2O)4(SO4)6] |
| 7.DF.52 | Scordariite | K8(Fe3+0.67◻0.33)[Fe3+3O(SO4)6]2 · 14H2O |
| 7.DF.55 | Clairite | (NH4)2Fe3(SO4)4(OH)3 · 3H2O |
| 7.DF.55 | Giacovazzoite | K5Fe3+3O(SO4)6 · 10H2O |
| 7.DF.57 | Magnanelliite | K3Fe3+2(SO4)4(OH)(H2O)2 |
| 7.DF.60 | Arzrunite | Cu4Pb2(SO4)(OH)4Cl6 · 2H2O (?) |
| 7.DF.60 | Evdokimovite | Tl4(VO)3(SO4)5(H2O)5 |
| 7.DF.62 | Bridgesite-(Ce) | CaCe2Cu6(SO4)4(OH)12 · 8H2O |
| 7.DF.65 | Elyite | Pb4Cu(SO4)O2(OH)4 · H2O |
| 7.DF.70 | Yecoraite | Fe3+3Bi5(Te6+O4)2(Te4+O3)O9 · 9H2O |
| 7.DF.70 | Lautenthalite | PbCu4(SO4)2(OH)6 · 3H2O |
| 7.DF.75 | Riomarinaite | Bi(SO4)(OH) · H2O |
| 7.DF.80 | Dukeite | Bi3+24Cr6+8O57(OH)6 · 3H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 15.7044% | 4,868 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Other Information
Notes:
Decomposed by water into epsomite and sylvite.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Kainite in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Kainite
mindat.org URL:
https://www.mindat.org/min-2132.html
Please feel free to link to this page.
Please feel free to link to this page.
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Mineral Dealers:
References for Kainite
Reference List:
Zepharovich, V. von (1882) Ueber Kainit, Rutil und Anatas. Zeitschrift für Krystallographie, Mineralogie und Petrographie, 6 (1-6). 234-243 doi:10.1524/zkri.1882.6.1.234
Robinson, Paul D., Fang, J. H., Ohya, and Y. (1972) The crystal structure of kainite. American Mineralogist, 57 (9-10) 1325-1332
Borisov, Artem S., Siidra, Oleg I., Ugolkov, Valery L., Kuznetsov, Alexey N., Firsova, Vera A., Charkin, Dmitri O., Platonova, Natalia V., Pekov, Igor V. (2022) Complex hydrogen bonding and thermal behaviour over a wide temperature range of kainite KMg(SO4)Cl⋅2.75H2O. Mineralogical Magazine, 86 (1) 37-48 doi:10.1180/mgm.2021.101
Localities for Kainite
Showing 75 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.
Africa | |
| Holwerda et al. (1968) |
Australia | |
| Wilson et al. (2014) |
Austria | |
| Exel (1993) |
Canada | |
| Shang (2000) |
Chile | |
| Pueyo et al. (2021) +1 other reference |
China | |
| Ju et al. (2019) |
| Shaoxiu (1991) |
| Bingxiao (1992) |
| Tang (2005) | |
| Bingxiao (1992) |
Czech Republic | |
| Matýsek et al. (2026) |
| Varilová et al. (2011) |
Germany | |
| Krah et al. (1988) |
| Weiß (1990) |
| Weiß (1990) |
| Weiß (1990) |
| Weiß (1990) |
| Weiß (1990) |
| Bode "Mineralien und Fundstellen BRD" ... +1 other reference |
| mrdata.usgs.gov (n.d.) |
| Aufschluss 1987 (4) |
| Jeff Weissman collection |
| Palache et al. (1951) |
| Naumann |
| Brockt et al. (2001) |
| C. Zinken (1865) +1 other reference |
| ... +1 other reference | |
| W.I. Borrisenkow (1968) |
Iceland | |
| Balić-Žunić et al. (2016) |
| Jakobsson et al. (1992) |
Iran | |
| Talbot et al. (2009) |
Italy | |
| Russo et al. (2022) |
| Kuehn R. (1972) +1 other reference |
| Adamo et al. (1979) +2 other references | |
| Lugli S. et al. (2006) |
| Adamo et al. (1979) +1 other reference |
| Mezzadri (1988) |
| Mezzadri (1988) | |
| Mezzadri (1988) |
| Adamo et al. (1979) +1 other reference | |
| Mezzadri (1988) |
| Mezzadri (1988) |
| Mezzadri (1988) | |
| Marella et al. (2006) +1 other reference | |
| Marella et al. (2006) +1 other reference | |
| Marella et al. (2006) +1 other reference | |
| Mezzadri (1988) | |
| Barbieri et al. (1968) +4 other references |
| Brescia et al. (2025) | |
| Roda (1970) +3 other references |
| Adamo et al. (1979) |
Kazakhstan | |
| ERCOSPAN (2011) |
| Pekov et al. (1993) |
Pakistan | |
| Ullah (1963) |
Poland | |
| Jirásek +7 other references |
| Wachowiak et al. (2012) |
Russia | |
| Tolstykh et al. (2021) |
| Pekov et al. (2015) |
| Palache et al. (1951) |
| Palache et al. (1951) |
Tunisia | |
| Smykatz-Kloss et al. (2010) |
UK | |
| Smith et al. (2014) |
| Smith et al. (2014) |
| Kemp et al. (2016) | |
Ukraine | |
| Bukowski +3 other references |
| Palache et al. (1951) | |
| BILONIZHKA (2003) |
USA | |
| Buck et al. (2006) |
| Palache et al. (1951) +1 other reference |
| Hawley +5 other references |
| Philip (2013) | |
| - (2005) | |
| Bullock (1981) |
| Bullock (1981) |
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Friedrichshall potash mine, Staßfurt, Salzlandkreis, Saxony-Anhalt, Germany