Carnallite is an
evaporitemineral, a hydrated potassium magnesium chloridewith 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 orthorhombiccrystals. It is transparent to translucent with a greasy luster. The refractive indices are nα=1.467 nβ=1.476 nγ=1.494. It has a Mohs hardnessof 2.5 and a specific gravityof 1.6. 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, polyhaliteand kieserite. Carnallite is a somewhat rare double chloride mineral which only forms under a 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 Basinin Coloradoand Utah; Stassfurt, Germany; the Perm Basin, Russia; and the Williston Basinin Saskatchewan, Canada. These deposits date from the Devonianthrough the PermianPeriods. In contrast, both Israeland Jordanproduce potashfrom the Dead Seaby using evaporation pans to further concentrate the brine until carnallite precipitates, dredging the carnallite from the pans, and processing to remove the magnesium chloridefrom the potassium chloride.
Carnallite was first described in 1856 from its type location of Stassfurt Deposit,
Saxony-Anhalt, Germany. It was named for the Prussian mining engineer, Rudolph von Carnall(1804-1874).
List of minerals
List of minerals named after people
* [http://www.mindat.org/min-906.html Mindat with location data]
* [http://webmineral.com/data/Carnallite.shtml Webmineral]
* [http://mineral.galleries.com/minerals/halides/carnalli/carnalli.htm Mineral galleries]
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