Hydrohalite is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

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, p ...

brines at cold temperatures (below 0.1 °C). It was first described in 1847 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 D ...

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

. It exists in cold weather. WatNaCl

Hydrohalite has a high nucleation energy, and solutions will normally need to be

supercooled Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its melting point without it becoming a solid. It achieves this in the absence of a seed crystal or nucleus around which a crystal ...

for crystals to form. The cryohydric point is at . Above this temperature, liquid water saturated with salt can exist in equilibrium with hydrohalite. Hydrohalite has a strong positive temperature coefficient of

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

, unlike halite. Hydrohalite decomposes at 0.1°C, giving a salty brine and solid halite. 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 gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

(for 1–1000 atmospheres). The maximum decomposition temperature is at 25.8°C under 9400 atmospheres. Above this pressure the decomposition point goes down.

Ceres

Hydrohalite was discovered on

Ceres Ceres most commonly refers to: * Ceres (dwarf planet), the largest asteroid * Ceres (mythology), the Roman goddess of agriculture Ceres may also refer to: Places Brazil * Ceres, Goiás, Brazil * Ceres Microregion, in north-central Goiás ...

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 information and dataHydrohalite Mineral Data
Halide minerals Sodium minerals Monoclinic minerals Minerals in space group 14 {{halide-mineral-stub