Halite

Halite (/ˈhæltˌ ˈhlt/ HAL-yte, HAY-lyte), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride (NaCl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on inclusion of other materials, impurities, and structural or isotopic abnormalities in the crystals. It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, and borates. The name halite is derived from the Ancient Greek word for "salt", ἅλς (háls).

Halite
Halite from the Wieliczka salt mine, Małopolskie, Poland
General
CategoryHalide mineral
Formula
(repeating unit)
NaCl
IMA symbolHl
Strunz classification3.AA.20
Crystal systemCubic
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFm3m
Unit cella = 5.6404(1) Å; Z = 4
Identification
Formula mass58.433 g/mol
ColorColorless or white when pure. Impurities produce any color but usually yellow, gray, black, brown, red (Depends on isotopes and purity for various colours)
Crystal habitPredominantly cubes and in massive sedimentary beds, but also granular, fibrous and compact
CleavagePerfect {001}, three directions cubic
FractureConchoidal
TenacityBrittle
Mohs scale hardness2.0–2.5
LusterVitreous
StreakWhite
DiaphaneityTransparent to Translucent
Specific gravity2.17
Optical propertiesIsotropic
Refractive indexn = 1.544
Melting point800.7 °C
SolubilityWater-soluble
Other characteristicsSalty flavor, fluorescent
References
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