Hydrohalite is a

halide mineral Halide minerals are those minerals with a dominant halide anion (, , and ). Complex halide minerals may also have Polyatomic ion, polyatomic anions. Examples include the following: *Atacamite *Avogadrite (K,Cs)BF *Bararite (β) *Bischofite * ...

that occurs in saturated

halite Halite ( ), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...

brines at cold temperatures (below 0.1 °C) and is the most common form of hydrated

sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...

. It was first described in 1847 from an occurrence in

Dürrnberg Dürrnberg, also named Bad Dürrnberg, is an Austrian village part of the municipality of Hallein, in Hallein District (Tennengau), Salzburg State. It is the location of the Hallein Salt Mine (''Salzbergwerk Dürrnberg''). History The history of ...

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

Physical properties

Hydrohalite has a high nucleation energy, it decomposes at 0.1°C, giving a salty brine and solid halite. WatNaCl

The cryohydric point of hydrohalite is at , solutions will normally need to be

supercooled Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid below its freezing point without it becoming a solid. Per the established international definition, supercooling means ''‘cooling a substance be ...

for crystals to form. Above this temperature, liquid water saturated with salt can exist in equilibrium with hydrohalite. Unlike

, hydrohalite has a strong positive temperature coefficient of

solubility In chemistry, solubility is the ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form su ...

. Under pressure, hydrohalite is stable between 7,900 and 11,600 atmospheres pressure. The decomposition point increases at the rate of 0.007K per

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

(for 1–1000 atmospheres), reaching a maximum decomposition temperature is at 25.8°C around 9400 atmospheres. The decomposition temperature reduces again at higher pressures.

Occurrence

The type locality is the

Hallein Salt Mine The Hallein Salt Mine, also known as ''Salzbergwerk Dürrnberg'', is an underground salt mine located in the Dürrnberg plateau above Hallein, Austria. The mine has been worked for over 2600 years since the time of the Celtic tribes and earlier. ...

.Page ''Hydrohalite: Mineral information, data and localities'' on

Ceres

Hydrohalite was discovered on Ceres by ''Dawn'',De Sanctis, M.C., Ammannito, E., Raponi, A. et al. Fresh emplacement of hydrated sodium chloride on Ceres from ascending salty fluids. Nat Astron 4, 786–793 (2020). https://doi.org/10.1038/s41550-020-1138-8 suggesting an early ocean, possibly surviving as a relict ocean.

References

Hydrohalite Mineral Data
Sodium minerals Chloride minerals Dihydrate minerals Monoclinic minerals Minerals in space group 14 Minerals described in 1847 {{halide-mineral-stub