Carnallite
A valid IMA mineral species - grandfathered
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About Carnallite
Rudolf von Carnall
Formula:
KMgCl3 · 6H2O
Colour:
Yellow to white, reddish, seldom white, colourless or blue.
Lustre:
Greasy
Hardness:
2½
Specific Gravity:
1.602
Crystal System:
Orthorhombic
Name:
Named in honor of Rudolf von Carnall (9 February 1804, Glatz, German Empire - 17 November 1874, Wroclaw, German Empire (now Poland)), mining engineer and geologist.
Type Locality:
Chemically and structurally related to novograblenovite.
A metastable monoclinic dimorph has been prepared as a synthetic phase (Pannach et al., 2020).
A metastable monoclinic dimorph has been prepared as a synthetic phase (Pannach et al., 2020).
Unique Identifiers
Mindat ID:
906
Long-form identifier:
mindat:1:1:906:1
IMA Classification of Carnallite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
KMgCl3·6H2O
First published:
1856
Classification of Carnallite
3.BA.10
3 : HALIDES
B : Simple halides, with H2O
A : M:X = 1:1 and 2:3
3 : HALIDES
B : Simple halides, with H2O
A : M:X = 1:1 and 2:3
11.1.2.1
11 : HALIDE COMPLEXES
1 : AmBX3
11 : HALIDE COMPLEXES
1 : AmBX3
8.4.5
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
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 |
|---|---|---|
| Cna | 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 Carnallite
Greasy
Transparency:
Transparent, Translucent
Colour:
Yellow to white, reddish, seldom white, colourless or blue.
Streak:
White
Hardness:
2½ on Mohs scale
Cleavage:
None Observed
Fracture:
Conchoidal
Density:
1.602 g/cm3 (Measured) 1.598 g/cm3 (Calculated)
Optical Data of Carnallite
Type:
Biaxial (+)
RI values:
nα = 1.465 - 1.466 nβ = 1.474 - 1.475 nγ = 1.494 - 1.496
2V:
Measured: 70° , Calculated: 66°
Max. Birefringence:
δ = 0.029 - 0.030
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 (negative)
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:
r < v
Chemistry of Carnallite
Mindat Formula:
KMgCl3 · 6H2O
Element Weights:
Common Impurities:
Br,Rb,Cs,Tl,Fe
Crystallography of Carnallite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pnna
Cell Parameters:
a = 16.119(3) Å, b = 22.472(4) Å, c = 9.551(2) Å
Ratio:
a:b:c = 0.717 : 1 : 0.425
Unit Cell V:
3,459.62 ų (Calculated from Unit Cell)
Z:
12
Morphology:
Crystals pseudo-hexagonal, pyramidal in habit, due to the substantially equant development of pyramids and brachydomes. Thick tabular with large {0001} at times. Massive, granular.
Twinning:
Secondary twinning lamellae. May exhibit polysynthetic twinning.
Crystal Structure
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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) |
|---|---|---|---|---|---|---|---|
| 0014748 | Carnallite | Fischer W (1973) Die kristallstruktur des carnallits KMgCl3*6H2O Neues Jahrbuch fur Mineralogie, Monatshefte 1973 100-109 | 1973 | synthetic | 0 | 293 | |
| 0001005 | Carnallite | Schlemper E O, Sen Gupta P K, Zoltai T (1985) Refinement of the structure of carnallite, Mg(H2O)6KCl3 American Mineralogist 70 1309-1313 |  | 1985 | 0 | 293 |
CIF Raw Data - click here to close
Epitaxial Relationships of Carnallite
Epitaxial Minerals:
| 'Hematite' | Fe2O3 |
Epitaxy Comments:
Hematite scales oriented with {0001} parallel to carnallite {001}, also parallel {110} or {100}.
X-Ray Powder Diffraction
Loading XRD data...
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.322 Å | (100) |
| 2.932 Å | (95) |
| 3.604 Å | (70) |
| 3.038 Å | (70) |
| 3.555 Å | (55) |
| 2.346 Å | (50) |
| 3.753 Å | (45) |
Comments:
ICDD 24-869.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] |
Geological Setting:
Saline marine deposits by action of high potash fluids.
Type Occurrence of Carnallite
Place of Conservation of Type Material:
No defined type material.
Geological Setting of Type Material:
Upper layers of saline deposits of the marine type.
Associated Minerals at Type Locality:
Other Language Names for Carnallite
Varieties of Carnallite
| Bromcarnallite | A Br-bearing carnallite. |
| Iodcarnallite | Artificial Iodine analogue of Carnallite |
Common Associates
Associations Based on Photo Data:
| 18 photos of Carnallite associated with Halite | NaCl |
| 12 photos of Carnallite associated with Sylvite | KCl |
| 7 photos of Carnallite associated with 'Shale' | |
| 5 photos of Carnallite associated with Rokühnite | FeCl2 · 2H2O |
| 4 photos of Carnallite associated with Anhydrite | CaSO4 |
| 3 photos of Carnallite associated with 'Sylvinite' | |
| 2 photos of Carnallite associated with Tachyhydrite | CaMg2Cl6 · 12H2O |
| 2 photos of Carnallite associated with 'Evaporite' | |
| 2 photos of Carnallite associated with Rinneite | K3Na[FeCl6] |
| 1 photo of Carnallite associated with Kieserite | MgSO4 · H2O |
Related Minerals - Strunz-mindat Grouping
| 3.BA.05 | Hydrohalite | NaCl · 2H2O |
| 3.BA.15 | Novograblenovite | (NH4)MgCl3 · 6H2O |
| 3.BA.20 | Cryobostryxite | KZnCl3 · 2H2O |
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) | 14.0715% | 4,362 | 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
Fluorescence of Carnallite
None.
Other Information
Notes:
Deliquescent. Soluble in water. The evaporated solution yields sylvite and bischofite.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Carnallite in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Carnallite
mindat.org URL:
https://www.mindat.org/min-906.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Carnallite
Reference List:
Rose, Heinr. (1856) Ueber den Carnallit. Annalen der Physik und Chemie, 174. 161-163 doi:10.1002/andp.18561740513
Lindberg, Marie Louise (1946) Occurrence of bromine in carnallite and sylvite from Utah and New Mexico. American Mineralogist, 31 (9-10) 486-494
King, R. H. (1946) Carnallite-filled mud cracks in salt clay [Carlsbad area, New Mexico]. Journal of Sedimentary Research, 16 (1) 14 doi:10.1306/d4269242-2b26-11d7-8648000102c1865d
Fischer, Werner (1973) Die Kristallstruktur des Carnallits KMgCl3·6H2O [The crystal structure of carnallite KMgCl3 • 6H2O]. Neues Jahrbuch für Mineralogie - Monatshefte, 1973 (3). p.100-109. doi:10.1127/njmm/1973/1973/100
Schlemper, E. O., Gupta, P. K. Sen, Zoltai, Tibor (1985) Refinement of the structure of carnallite, Mg(H2O)6KCl3. American Mineralogist, 70 (11-12) 1309-1313
Casas, Enrique; Lowenstein, Tim K.; Spencer, Ronald J.; Pengxi, Zhang (1992) Carnallite Mineralization in the Nonmarine, Qaidam Basin, China: Evidence for the Early Diagenetic Origin of Potash Evaporites. SEPM Journal of Sedimentary Research, 62. p.881-898. doi:10.1306/d4267a05-2b26-11d7-8648000102c1865d
Zhao, Xian-Fu, Wang, Zong-Qi, Qiu, Jun-Ting, Song, Yang (2016) Reflectance Spectral Characteristics of Minerals in the Mboukoumassi Sylvite Deposit, Kouilou Province, Congo. Minerals, 6 (2). 55pp. doi:10.3390/min6020055(detailed data on carnallite)
Pannach, Melanie, Paschke, Iris, Schmidt, Horst, Freyer, Daniela, Voigt, Wolfgang (2020) Crystallization of metastable monoclinic carnallite, KCl·MgCl2·6H2O: missing structural link in the carnallite family. Acta Crystallographica Section C Structural Chemistry, 76 (5). 507-512 doi:10.1107/s2053229620005197
Localities for Carnallite
Showing 173 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) |
Belarus | |
| Russian Journal of Earth Sciences Vol. 6 |
| Russian Journal of Earth Sciences Vol. 6 +1 other reference |
Bolivia | |
| Kempff et al. (La Paz, 2009) |
Brazil | |
| da Silva et al. (2000) | |
| www.cetem.gov.br (n.d.) +1 other reference |
Canada | |
| B.B. Bannatyne (1983) |
| B.B. Bannatyne (1983) | |
| Grice et al. (2005) |
| Boehner (1986) |
| Sabina (2003) |
| Grice (1989) |
| 152. +3 other references | |
| Shang (2000) | |
| King et al. (1993) |
| Funk et al. (2021) |
Chile | |
| Pueyo et al. (2021) +1 other reference |
China | |
| Sun Da-peng et al. (2002) +1 other reference |
| Xiyu Zheng (1994) +2 other references |
| Warren (2010) |
| Dongsheng Hu (1990) +3 other references |
| Botao Li et al. (2010) +1 other reference | |
| Jianqi Yuan and Zhenhao Duan (1989) +1 other reference | |
| Jianqi Yuan and Zhenhao Duan (1989) | |
| Shaoxiu (1991) +2 other references |
| Shaoxiu (1991) | |
| Shaoxiu (1991) +1 other reference |
| Xiying Zhang et al. (2007) | |
| Shaoxiu (1991) | |
| Yuhua Chen et al. (1998) | |
| Tang (2005) |
| Tang (2005) |
| Bingxiao (1992) +1 other reference | |
| Lichun Ma et al. (2010) | |
| Tang (2005) | |
| Bingxiao (1992) |
| Xiaosong Xu and Jialing Wu (1983) +4 other references |
Czech Republic | |
| Matýsek et al. (2026) |
Egypt | |
| BORCHERT et al. (801-864) +2 other references |
Ethiopia | |
| Hovland et al. (2018) |
| Palache et al. (1951) +1 other reference | |
Eurasian Plate | |
| Ding et al. (2026) | |
| Wang et al. (2017) | |
Germany | |
| Weiß (1990) |
| |
| Weiß (1990) |
| Weiß (1990) |
| Niemann (1960) |
| |
| Weiß (1990) |
| Bode "Mineralien und Fundstellen BRD" ... +1 other reference |
| mrdata.usgs.gov (n.d.) |
| George Graf collection |
| Weiß (1990) |
| Aufschluss 1987 (4) |
| Palache et al. (1951) |
| www.mineralienatlas.de (n.d.) |
| www.mineralienatlas.de (n.d.) |
| |
| |
| Palache et al. (1951) | |
| Palache et al. (1951) |
| Brockt et al. (2001) |
| Palache et al. (1951) +1 other reference | |
| Naumann +1 other reference | |
| ... | |
| Horst (1989) |
| de.wikipedia.org (n.d.) |
| Effmert +1 other reference |
| Effmert et al. (2007) | |
| BOEKE (1909) | |
| Leon Hupperichs collection | |
| www.harzergruben.de (n.d.) |
| |
Iceland | |
| Jakobsson et al. (1992) |
Italy | |
| Pellino et al. (2025) |
| Adamo et al. (1979) |
| Adamo et al. (1979) | |
| Lugli S. et al. (2006) |
| Mezzadri (1988) |
| Mezzadri (1988) | |
| Mezzadri (1988) |
| Mezzadri (1988) |
| Mezzadri (1988) |
| Mezzadri (1988) | |
| Marella et al. (2006) +1 other reference | |
| Mezzadri (1988) | |
| Roda (1970) +3 other references |
| Roda (1970) +4 other references |
Kazakhstan | |
| ERCOSPAN (2011) |
| Pavel M. Kartashov (n.d.) +1 other reference |
| Pekov (1998) +1 other reference |
| Pekov et al. (2020) | |
Laos | |
| Xiying Zhang et al. (2010) +1 other reference |
Netherlands | |
| T.G. Nijland |
| T.G. Nijland |
| Pichat (2022) | |
New Zealand | |
| Railton et al. (1990) |
North Sea | |
Poland | |
| Jirásek +7 other references |
| Praszkier (2010) |
Portugal | |
| 11.1.2.1 |
Republic of the Congo | |
| de Ruiter (1979) |
| Zhao et al. (2016) |
| Henry Rauche (2009) | |
| Milesi et al. (2006) | |
Russia | |
| Pekov (1998) |
| Seltmann et al. (2010) +1 other reference |
| Mazurov et al. (2007) |
| Pekov et al. (2015) |
| Пекин (2010) +1 other reference | |
| Pavel M. Kartashov (n.d.) +2 other references |
| Chaikovskiy et al. (2019) +1 other reference |
| Vergasova et al. (1977) +1 other reference |
| Palache et al. (1951) |
Spain | |
| Sánchez-España et al. (2024) |
| Carles Curto Milà. |
| Calvo Rebollar (2006) +1 other reference |
| Calvo Rebollar (2006) | |
| Calvo Rebollar (2006) |
| Calvo Rebollar (2006) |
Thailand | |
| Tabakh et al. (1998) |
| Suwanich (2010) |
Tunisia | |
| Smykatz-Kloss et al. (2010) |
Turkmenistan | |
| Yongsheng Zhang et al. (2005) |
| Yongsheng Zhang et al. (2005) |
UK | |
| Milne (1978) +1 other reference |
| Armstrong et al. (1951) |
| Armstrong et al. (1951) | |
| Armstrong et al. (1951) | |
Ukraine | |
| Bukowski +2 other references |
USA | |
| Peirce (1969) +1 other reference |
| Eckel et al. (1997) |
| Heinrich et al. (2004) |
| Heinrich et al. (2004) |
| Northrop et al. (1996) |
| Hawley +5 other references |
| Philip (2013) | |
| King (n.d.) +1 other reference | |
| - (2005) | |
| Jeff Weissman | |
| - (2005) |
| - (2005) |
| - (2005) | |
| - (2005) |
| Bullock (1981) | |
| Bullock (1981) |
| Bullock (1981) | |
| - (2005) |
| - (2005) | |
| Bullock (1981) | |
| Bullock (1981) | |
| - (2005) |
| - (2005) | |
| - (2005) | |
| Bullock (1981) |
| - (2005) |
| Bullock (1981) | |
| Bullock (1981) | |
| - (2005) |
| - (2005) | |
| - (2005) | |
| - (2005) |
| Bullock (1981) | |
| - (2005) |
| - (2005) | |
| - (2005) | |
| - (2005) | |
| - (2005) |
| - (2005) | |
| - (2005) | |
| Bullock (1981) |
Quick NavTopAbout CarnalliteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureEpitaxial Relationships X-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesVarietiesCommon AssociatesStrunz-MindatRadioactivityFluorescence Other InformationCarnallite in petrologyInternet Links References Localities Locality List
Mulhouse potash mining district, Haut-Rhin, Grand Est, France