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Formula: KMgCl3.6H2O
Chloride
Crystal System: Orthorhombic
Specific gravity: 1.602 measured, 1.598 calculated
Hardness: 2½
Streak: White
Colour: Yellow to white, reddish, seldom white, colourless or blue
Solubility: Soluble in water, deliquescent
Common impurities: Br,Rb,Cs,Tl,Fe
Environments
Carnallite is thought to form in saline marine deposits by reaction of pre-existing saline minerals with
fluids high in potash. Associated minerals include kieserite,
sylvite, halite,
polyhalite and bischofite
(HOM)
Carnallite forms an epiaxial relationship with hematite, with
hematite scales oriented with {0001} parallel to carnallite {001},
also parallel {110} or {100}
(Mindat).
Localities
At the type locality, Stassfurt, Stassfurt Potash deposit, Saxony-Anhalt, Germany, carnallite occurs in upper
layers of the saline deposits associated with sylvite,
polyhalite, kieserite and
halite
(Mindat).
At Eddy county, New Mexico, USA, drill cores contained predominantly colourless
halite, brick-red sylvite and
blood-red carnallite, with lesser amounts of pink polyhalite, white
kieserite, anhydrite, and red or
grey clay
(AM 31.486-494).
At McCarthy, No. 1 well, Grand county, Utah, USA, in drill cores halite is the
most abundant mineral. It is colourless or grey, medium-grained, and with interIocking grains. Carnallite
and sylvite are also abundant, and
kieserite, anhydrite and
clay are present in small quantities
(AM 31.486-494).
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