Carnallite (also carnalite) is an evaporite mineral, a hydrated potassium magnesium chloride with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare pseudohexagonal orthorhombic crystals. The mineral is deliquescent (absorbs moisture from the surrounding air) and specimens must be stored in an airtight container.

Carnallite occurs with a sequence of potassium and magnesium evaporite minerals: sylvite, kainite, picromerite, polyhalite, and kieserite. Carnallite is an uncommon double chloride mineral that only forms under specific environmental conditions in an evaporating sea or sedimentary basin. It is mined for both potassium and magnesium and occurs in the evaporite deposits of Carlsbad, New Mexico; the Paradox Basin in Colorado and Utah; Stassfurt, Germany; the Perm Basin, Russia; and the Williston Basin in Saskatchewan, Canada. These deposits date from the Devonian through the Permian Periods. In contrast, both Israel and Jordan produce potash from the Dead Sea by using evaporation pans to further concentrate the brine until carnallite precipitates, dredging the carnallite from the pans, and processing to remove the magnesium chloride from the potassium chloride.[4]

Carnallite was first described in 1856 from its type location of Stassfurt Deposit, Saxony-Anhalt, Germany. It was named for the Prussian mining engineer Rudolf von Carnall (1804–1874).[4]

Carnallite from Russia
Carnallit cristalls
Сarnallite crystals
CategoryHalide mineral
(repeating unit)
Strunz classification3.BA.10
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnna
Formula mass277.85 g/mol
ColorBlue, colorless, yellow, white, red
Crystal habitFibrous
TwinningBy pressure, polysynthetic twin lamellae can be developed
Mohs scale hardness2.5
DiaphaneityTransparent to translucent
Specific gravity1.6
Density1.598 g/cm3
Optical propertiesBiaxial (+)
Refractive indexnα = 1.467
nβ = 1.476
nγ = 1.494
2V angle70

Background Information

Halides are binary compounds. They are composed of a halogen and a metal ion. The crystal chemistry of halides is characterized by the electronegativity of halogen ions.[5] This means that the dominant large ions are the Cl, Br, F, or I. These are easily polarized.[5][6] The ions combine with similarly large but low valence and weakly polarized cations. The cations are mostly of the alkali metal group. Sylvite is a binary compound with the formula KCl. Sylvite precipitates first from mixed solutions of K+, Mg2+ and Cl, leaving a brine enriched in magnesium from which the mixed halide carnallite then precipitates.[5]


Carnallite’s chemical formula is KMgCl3·6(H2O). Synthetic carnallite crystal specimens can be produced from 1.5 mole percent KCl and 98.5 mole percent MgCl2·6H2O by slow crystallization at 25 °C.[7] Its density is 1.602 g/cm3.[7] Carnallite can also be produced by grinding the combination of hydrated magnesium chloride and potassium chloride.[8]


Carnallite has corner- and face-sharing. There is a network of KCl6 octahedra, with two-thirds of them sharing faces.[7] Mg(H2O)6 octahedra occupy the open spaces within the KCl octahedra. The interatomic distance between the Mg and the H2O ranges from 0.204 to 0.209 nm.,[7] with an average is 0.2045 nm.[7] The interatomic distance between K and Cl ranges 0.317 to 0.331 nm.,[7] with an average of 0.324 nm.[7] The resulting structure has a calculated density of 1.587 g/cm3, in good agreement with the measured value of 1.602 g/cm3.[7]

Face sharing creates more chance of instability, according to the third of Pauling's rules.[6] In carnallite, the water molecules enclose the magnesium ions. This prevents the magnesium and the chloride from interacting directly; instead, the water molecules act as charge transmitters.[7] The five chloride anions are each coordinated to two potassium cations as well as four water molecules.[7] This means that each chloride anion receives 1/6 of a +1 charge from each of the two potassium ions. The chloride also obtains 1/6 of a +1 charge from each the four water molecules. The charges thus total six 1/6 positive charges, which balance the negative charge of the chloride. These two aspects render the rare face sharing described of the second and third of Pauling’s rule acceptable in the carnallite structure.[6][7]

Physical properties

Carnallite’s refractive index ranges from 1.467 to 1.494.[6][9] Carnallite may be red as a result of hematite (Fe2O3) inclusions.[9] The fragmented shards of iron oxide produce red tints in the thin laminae of hematite.[9] Carnallite is also deliquescent in high humidity. This implies that it is also extremely soluble in water.[9] Individual crystals are pseudo-hexagonal and tabular but are extremely rarely seen.[10] Field indicators of carnallite are environment of formation, absence of cleavage, and fracture. Other indicators can be density, taste, associations to local minerals, and whether it is capable of luminescence. Carnallite has a bitter taste.[10] Carnallite may not only be fluorescent but is capable of being phosphorescent.[10] The potassium that carnallite contains fuses easily within a flame, creating a violet color.[10]

Geologic occurrence

Mineral associations based on some physical properties include, but not limited to, halite, anhydrite, dolomite, gypsum, kainite, kieserite, polyhalite, and sylvite.[6][11][12]

Carnallite is found in saline marine deposits.[10] Carnallite minerals are mineral sediments known as evaporites. Evaporites are concentrated by evaporation of seawater. The inflow of water must be below the evaporation or use levels. This creates a prolonged evaporation period. In controlled environment experiments, the halides form when 10%–20% of the original sample of water remains.[13] Closer to 10 percent sylvite followed by Carnallite form.[13]


Carnallite is mostly used in fertilizers. It is an important source of potash.[12] Only sylvite outranks carnallite’s importance in potash production.[12] Both are uncommon because they are some of the last evaporites to form.[12] Soluble potassium salts are the main sources for fertilizer. This is because the potassium is difficult to separate from insoluble potassium feldspar.[12] Carnallite is a minor source of magnesium worldwide; however, it is Russia’s main source.[12]

See also


  1. ^ Mineralienatlas
  2. ^ Webmineral data
  3. ^ Handbook of Mineralogy
  4. ^ a b c Carnallite on Mindat
  5. ^ a b c Bragg, L., and G. F. Claringbull. (1965) Crystal Structure of minerals. G. Bell and Sons, Ltd., London.
  6. ^ a b c d e Klein, Cornelis, B. Dutrow (2007) Manual of Mineral Science, 23rd ed.John Wiley and Sons
  7. ^ a b c d e f g h i j k Schlemper, E. O., P. K. Gupta, and Tibor Zoltai. (1985) Refinement of the Structure of Carnallite, Mg(H2O)6KCL3. American Mineralogist 70,1309-1313.
  8. ^ Shoval, S., S. Yariv. (1998) Formation of Carnallite Type Double Salts by Grinding Mixtures of Magnesium and Alkali Halides with the Same Anions. Journal of Thermal Analysis 51, 251-263
  9. ^ a b c d Mottana, Annibale, R. Crespi, and G. Liborio. (1978) Rocks and Minerals. Simon and Schuster. NY.
  10. ^ a b c d e Blatt, H. (1992) Sedimentary Petrology, 2nd ed. W.H. Freeman and Co., San Francisco.
  11. ^ Anthony, J. W., R. A. Bideaux, R. A., Bladh, K. W. and M. C. Nichols. (1997) Handbook of Mineralogy. Vol. 3 Halides, hydroxides, oxides. Mineral Data Publications, Tucson, Arizona.
  12. ^ a b c d e f Phosphate, potash, and sulfur- A special issue. (1979) Economic Geology 74, 191-493.
  13. ^ a b Smetannikov, A. F., (2010) Hydrogen Generation during the Radiolysis of Crystallization water in Carnallite and Possible Consequences of this Process Geochemistry International 49, 971-980
Abraum salts

Abraum salts is the name given to a mixed deposit of salts, including halite (sodium chloride), carnallite, and kieserite (magnesium sulfate), found in association with rock salt at Aschersleben-Staßfurt in Germany. The term comes from the German Abraum-salze, "salts to be removed."Abraum, which is red, is used to darken mahogany.

Americas Petrogas

Americas Petrogas Inc is a Canadian-based exploration and oil production company focused in Argentina's Neuquén Basin where it is one of the largest land owners, with 960,000 net acres spread over 12 large blocks of which 9 blocks are located in the Vaca Muerta shale corridors. Recently, Ryder Scott Company petroleum engineers assessed the Company with 7.6 Billion BOE P50 Best Case Unrisked Prospective (Recoverable) Shale Resources (Lower Agrio, Vaca Muerta, Los Molles). Americas Petrogas was sought out by ExxonMobil and others, to partner on its shale blocks. Subsequently, Americas Petrogas entered into a joint venture with ExxonMobil on 4 of its 9 shale blocks with Americas Petrogas retaining Operatorship. Together the partners have announced 3 successful Vaca Muerta discoveries.

Subsidiary GrowMax Agri Corp is exploring and developing a large phosphate and potash and carnallite fertilizer project in Northern Peru's Sechura Desert adjacent to Vale's Bayovar surface phosphate mine. Vale's partners in this venture include Mitsui and Mosaic.

Arab Potash

The Arab Potash Company (APC) is a company that is primarily involved in harvesting minerals from the Dead Sea. It is the eighth largest potash producer worldwide by volume of production and the sole Arab producer of potash. The Company was formed in 1956 in the Hashemite Kingdom of Jordan as a pan-Arab business venture and it has a 100-year concession (1958-2058) from the government of Jordan that grants it exclusive rights to extract, manufacture and market minerals from the Dead Sea. It is headquartered in Amman and has its main plants at Ghor Al Safi. The company's stock is listed on the Amman Stock Exchange's ASE Weighted Index.


Balsareny is a municipality in the North of the comarca of Bages in the province of Barcelona, Catalonia, Spain. It is situated in the valley of the river Llobregat, with its typical forests of Aleppo pines. It is connected by road (BP-4313) with Súria and Avinyó.

The name is thought to be derived from the Catalan words balç (escarpment) and areny (sand); the castle and the village have their origins on an escarpment in a sandy plane. The first written mention of the settlement (as pago bazarenensi) dates from 966.The village developed around the castle, which was built at a strategic point at the confluence of the river Mujal with the Llobregat, but most people lived in dispersed masias (farms). At the end of the 16th century, Baron Ferran Oliver sold some land around the castle and three streets were created: Carrer Vell (Old Street, nowadays Àngel Guimerà), Carrer Nou (New Street) and Carrer de la Creu (Cross street). A sanctuary dedicated to Mary is documented since 1009. The romanesque Church of St. Mary dates from late 13th century, but the building has undergone many transformations since then. The town was walled, but with the increase of population, new streets were added outside the walls.In the 19th century the walls were demolished and the roads were improved. Along with the Manresa-Berga railway (1885, closed down 1973), this contributed toward a flourishing textile industry, though this has now almost disappeared. In 1945 the extraction of the rich layers of potassium salts (sylvite and carnallite) started, and today this remains a major employer, but many other small and medium enterprises have also been created. There is also one of the major European production plants from Gates Corporation, an American manufacturer of power transmission belts and fluid power, employing about 240 people.


Bischofite (bischofit) is a hydrous magnesium chloride mineral with formula MgCl2·6H2O. It belongs to halides and is a sea salt concentrate. Bischofite is ecologically pure natural magnesium poly-mineral with a unique composition. It contains many macro- and micro-elements vital for human health, in much higher concentrations than can be found in sea or ocean salt. The main bischofit compound is magnesium chloride (up to 350 g/L), moreover, it contains about 70 other elements as impurities, including potassium, sodium, bromine, boron, calcium, silicon, molybdenum, silver, zinc, iron and copper.


Boracite is a magnesium borate mineral with formula: Mg3B7O13Cl. It occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic - pyramidal crystal system. Boracite also shows pseudo-isometric cubical and octahedral forms. These are thought to be the result of transition from an unstable high temperature isometric form on cooling. Penetration twins are not unusual. It occurs as well formed crystals and dispersed grains often embedded within gypsum and anhydrite crystals. It has a Mohs hardness of 7 to 7.5 and a specific gravity of 2.9. Refractive index values are nα = 1.658 - 1.662, nβ = 1.662 - 1.667 and nγ = 1.668 - 1.673. It has a conchoidal fracture and does not show cleavage. It is insoluble in water (not to be confused with borax, which is soluble in water).

Boracite is typically found in evaporite sequences associated with gypsum, anhydrite, halite, sylvite, carnallite, kainite and hilgardite. It was first described in 1789 for specimens from its type locality of Kalkberg hill, Lüneburg, Lower Saxony, Germany. The name is derived from its boron content (19 to 20% boron by mass).

Caesium chloride

Caesium chloride or cesium chloride is the inorganic compound with the formula CsCl. This colorless solid is an important source of caesium ions in a variety of niche applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chlorine ions. Caesium chloride dissolves in water. CsCl changes to NaCl structure on heating. Caesium chloride occurs naturally as impurities in carnallite (up to 0.002%), sylvite and kainite. Less than 20 tonnes of CsCl is produced annually worldwide, mostly from a caesium-bearing mineral pollucite.Caesium chloride is widely used medicine structure in isopycnic centrifugation for separating various types of DNA. It is a reagent in analytical chemistry, where it is used to identify ions by the color and morphology of the precipitate. When enriched in radioisotopes, such as 137CsCl or 131CsCl, caesium chloride is used in nuclear medicine applications such as treatment of cancer and diagnosis of myocardial infarction. Another form of cancer treatment was studied using conventional non-radioactive CsCl. Whereas conventional caesium chloride has a rather low toxicity to humans and animals, the radioactive form easily contaminates the environment due to the high solubility of CsCl in water. Spread of 137CsCl powder from a 93-gram container in 1987 in Goiânia, Brazil, resulted in one of the worst-ever radiation spill accidents killing four and directly affecting more than 100,000 people.

Chemische Fabrik Kalk

Chemische Fabrik Kalk (CFK) (lit. Chemical Factory Kalk) was a German chemicals company based in Kalk, a city district of Cologne. The company was founded in 1858 as Chemische Fabrik Vorster & Grüneberg, Cöln by Julius Vorster and Hermann Julius Grüneberg and was renamed to Chemische Fabrik Kalk GmbH in 1892. At times the company was the second-largest German producer of soda ash and was, with almost 2400 employees, one of the largest employers in Cologne. For decades the chimneys and the water tower of the factory dominated the skyline of Cologne-Kalk.

In 1960 the company was acquired by the Salzdetfurth AG, which was later renamed into Kali und Salz (nowadays K+S) and became a subsidiary of BASF. All production facilities of the former Chemische Fabrik Kalk were closed in 1993, and the name Chemische Fabrik Kalk since then exists only as the name of a wholesale subsidiary of K+S. The factory was demolished and after the decontamination of the premises the new Cologne police departments headquarters and the Köln Arcaden shopping mall were built on the former factory premises.


Evaporite ( ) is the term for a water-soluble mineral sediment that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean deposits, and non-marine, which are found in standing bodies of water such as lakes. Evaporites are considered sedimentary rocks and are formed by chemical sediments.

Gamma ray logging

Gamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole or drill hole. It is a wireline logging method used in mining, mineral exploration, water-well drilling, for formation evaluation in oil and gas well drilling and for other related purposes. Different types of rock emit different amounts and different spectra of natural gamma radiation. In particular, shales usually emit more gamma rays than other sedimentary rocks, such as sandstone, gypsum, salt, coal, dolomite, or limestone because radioactive potassium is a common component in their clay content, and because the cation exchange capacity of clay causes them to adsorb uranium and thorium. This difference in radioactivity between shales and sandstones/carbonate rocks allows the gamma ray tool to distinguish between shales and non-shales. But it cannot distinguish between carbonates and sandstone as they both have similar deflections on the gamma ray log. Thus gamma ray logs cannot be said to make good lithological logs by themselves, but in practice, gamma ray logs are compared side-by-side with stratigraphic logs.

The gamma ray log, like other types of well logging, is done by lowering an instrument down the drill hole and recording gamma radiation variation with depth. In the United States, the device most commonly records measurements at 1/2-foot intervals. Gamma radiation is usually recorded in API units, a measurement originated by the petroleum industry. Gamma rays attenuate according to the diameter of the borehole mainly because of the properties of the fluid filling the borehole, but because gamma logs are generally used in a qualitative way, amplitude corrections are usually not necessary.

Three elements and their decay chains are responsible for the radiation emitted by rock: potassium, thorium and uranium. Shales often contain potassium as part of their clay content and tend to adsorb uranium and thorium as well. A common gamma-ray log records the total radiation and cannot distinguish between the radioactive elements, while a spectral gamma ray log (see below) can.

For standard gamma-ray logs, the measured value of gamma-ray radiation is calculated from concentration of uranium in ppm, thorium in ppm, and potassium in weight percent: e.g., GR API = 8 × uranium concentration in ppm + 4 × thorium concentration in ppm + 16 × potassium concentration in weight percent. Due to the weighted nature of uranium concentration in the GR API calculation, anomalous concentrations of uranium can cause clean sand reservoirs to appear shaley. For this reason, spectral gamma ray is used to provide an individual reading for each element so that anomalous concentrations can be found and properly interpreted.

An advantage of the gamma log over some other types of well logs is that it works through the steel and cement walls of cased boreholes. Although concrete and steel absorb some of the gamma radiation, enough travels through the steel and cement to allow for qualitative determinations.

In some places, non-shales exhibit elevated levels of gamma radiation. For instance, sandstones can contain uranium minerals, potassium feldspar, clay filling, or lithic fragments that cause the rock to have higher than usual gamma readings. Coal and dolomite may contain adsorbed uranium. Evaporite deposits may contain potassium minerals such as sylvite and carnallite. When this is the case, spectral gamma ray logging should be done to identify the source of these anomalies.

Halide minerals

The halide mineral class include those minerals with a dominant halide anion (F−, Cl−, Br− and I−). Complex halide minerals may also have polyatomic anions in addition to or that include halides.

Examples include the following:

Atacamite Cu2Cl(OH)3

Avogadrite (K,Cs)BF

Bararite (ß)(NH4)2SiF6

Bischofite (MgCl2·6H2O)

Brüggenite Ca(IO3)2(H2O)

Calomel HgCl

Carnallite KMgCl3·6H2O

Carnallite KMgCl·6H2O

Cerargyite/Horn Silver AgCl

Chlorargyrite AgCl, bromargyrite AgBr, and iodargyrite AgI

Cryolite Na3AlF6

Cryptohalite (a)(NH4)2SiF6

Dietzeite Ca2(IO3)2CrO4

Eglestonite Hg4OCl2

Embolite AgCl+AgBr

Eriochalcite CuCl2·2H2O

Fluorite CaF2

Halite NaCl

Lautarite Ca(IO3)2

Marshite CuI

Miersite AgI

Nantokite CuCl

Sal Ammoniac NH4Cl

Sylvite KCl

Terlinguaite Hg2OCl

Tolbachite CuCl2

Villaumite NaF

Yttrocerite (Ca,Y,Ce)F2

Yttrofluorite (Ca,Y)F2

Many of these minerals are water-soluble and are often found in arid areas in crusts and other deposits as are various borates, nitrates, iodates, bromates and the like. Some, such as the fluorite group, are not water-soluble. All or most of simple halides of fluorine through iodine of all of the natural alkali metals and alkaline earth metals as well as numerous other metals and cations are found in some quantity at one or more locations. More complex minerals as shown below are also found.


Hygroscopy is the phenomenon of attracting and holding water molecules from the surrounding environment, which is usually at normal or room temperature. This is achieved through either absorption or adsorption with the adsorbing substance becoming physically changed somewhat. This could be an increase in volume, boiling point, viscosity, or other physical characteristic or property of the substance, as water molecules can become suspended between the substance's molecules in the process.


Kieserite is the magnesium sulfate mineral (MgSO4·H2O) and is named after Dietrich Georg von Kieser (Jena, Germany 1862). It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic crystal system. Gunningite is the zinc member of the kieserite group of minerals.

Labeling of fertilizer

Many countries have standardized the labeling of fertilizers to indicate their contents of major nutrients. The most common labeling convention, the NPK or N-P-K label, shows the amounts of the chemical elements nitrogen, phosphorus, and potassium.


Langbeinite is a potassium magnesium sulfate mineral with the chemical formula K2Mg2(SO4)3. Langbeinite crystallizes in the isometric-tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and the specific gravity is 2.83. The crystals are piezoelectric.The mineral is an ore of potassium and occurs in marine evaporite deposits in association with carnallite, halite and sylvite.It was first described in 1891 for an occurrence in Wilhelmshall, Halberstadt, Saxony-Anhalt, Germany, and named for A. Langbein of Leopoldshall, Germany.Langbeinite gives its name to the langbeinites, a family of substances with the same cubic structure, a tetrahedral anion, and large and small cations.

Related substances include hydrated salts leonite (K2Mg(SO4)2·4H2O) and picromerite (K2Mg(SO4)2·6H2O).

List of gemstones by species

This is a list of gemstones, organized by species and type.

Magnesite in Greece

Magnesium (Mg) is a chemical element, an alkaline earth metal, the eighth-most abundant element in the Earth's crust and the fourth-most common element on Earth. It is contained in magnesite, dolomite, brucite, carnallite, talc, and magnesium minerals. China is now the biggest producer of crude magnesite in the world for refractory and agricultural uses.

Crude magnesite was produced in Greece in 1910. It was first found in Atalanti and in the Province of Lokris, central Greece.

Other localities were Perachori, near Corinth; Ermioni (or Kastri) and on Spetses Island in southern Argolis in the Peloponnese; on Paros Island (Cyclades); around Thebes in Boeotia and in Papades and Troupi in northern Euboea. Euboea was mostly worked until the 1980s.

Galataki (near Limni) and Afrati (near Chalcis) were exploited by the English company Petrified Ltd. (founded 1897 and based in London), which finally sold its assets to the Anglo-Greek Magnesite Company. Ltd (AGM) in 1902. Besides, northern Greece was found to have magnesite mining interest, in the concessions of Aghia Paraskevi (east of Thessaloniki) in small production, and in Chalkidiki’s concessions of Vavdos,


and Yerakini with the largest deposits.

Magnesium bromide

Magnesium bromide (MgBr2) is a chemical compound of magnesium and bromine that is white and deliquescent. It is often used as a mild sedative and as an anticonvulsant for treatment of nervous disorders. It is water-soluble and somewhat soluble in alcohol. It can be found naturally in small amounts in some minerals such as: bischofite and carnallite, and in sea water, such as that of the Dead Sea.


Sylvinite is a sedimentary rock made of a mechanical mixture of the minerals sylvite (KCl, or potassium chloride) and halite (NaCl, or sodium chloride). Sylvinite is the most important source for the production of potash in North America, Russia and the UK. Most Canadian operations mine sylvinite with proportions of about 31% KCl and 66% NaCl with the balance being insoluble clays, anhydrite and in some locations carnallite. Other deposits of sylvinite are in Belarus, Brazil, France, Germany, Kazakhstan, Slovakia and Spain.

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