halite

1. A colorless or white mineral, NaCl, occurring as cubic crystals and found in dried lakebeds in arid climates, mined or gathered for use as table salt.
2. Rock salt.

For more information on halite, visit Britannica.com.

One of the group of minerals referred to as evaporites, halite is commonly known as salt. Halite is one of many substances that are essential for human life. Evaporite minerals form when ions are concentrated to their saturation point by the progressive evaporation of seawater or saline lake water. Halite precipitates after calcium sulfate, but before the highly soluble salts of potassium and magnesium. See also Halogen minerals; Saline evaporites.

Halite (chemical formula NaCl) is composed of sodium cations and chlorine anions in equal proportion. It is the most common chloride mineral in natural sequences which proceed beyond the precipitation of sulfates. Even in sequences which contain a high percentage of potassium and magnesium salts, halite is often the most common chloride present.

Crystals of halite are generally cubic or hopper-shaped (skeletal). Although the mineral is colorless generally, impurities can color it gray, red, orange, or brown. Blue or violet halit results from exposure to radioactivity, which produces dislocations and defects in the crystal structure. Halite is characterized by a hardness of 2.5 on Mohs scale and a specific gravity o 2.16.

The deformation of bedded halite deposits is of importance to the petroleum industry. Salt rises, in part as a result of density contrasts, to form domelike structures. Hydrocarbons (oil and gas) are commonly associated with salt domes. Exploration for these structures by geophysical techniques often results in major discoveries by the petroleum industry. See also Geophysical exploration; Petroleum geology; Salt dome.

Environment

Dried lakes in arid climates; buried sedimentary beds.

Commonly in cubic crystals, often distorted with hopperlike depressions in each cube face; also massive and granular, like marble; sometimes in large, cleavable, single crystal masses. Sometimes fibrous.

Colorless, white, sometimes reddish (from impurities), blue or violet (see Remarks). Luster glassy; hardness 2Ɖ; specific gravity 2.1-2.6; fracture conchoidal; cleavage perfect cubic. Brittle, flows slowly under great pressure; transparent; water-soluble; sometimes red fluorescent.

Sodium chloride (39.4% Na, 60.6% Cl).

Readily soluble in water, tastes salty. Colors flame yellow (sodium).

The salty taste should be enough. Distinguished from other salty-tasting minerals by the sodium flame (sharper-tasting sylvite is KCl) and from some water-soluble sulfates by the perfect cubic cleavage.

Halite is sometimes a part of the white crusts around gas vents in volcanic regions, but the important occurrences that would classify it as a one-mineral rock are the sedimentary beds interstratified with other sediments, formed in ancient geological time by the evaporation of closed saltwater basins. These rock salt strata are associated with gypsum and other sedimentary formations. Salt layers may flow under pressure and squeeze up through weak places, making pluglike formations of solid salt (the salt domes of the Gulf Coast). Salt is recovered by mining, or by introducing water to dissolve the salt beds and pumping this brine up through wells from the depths.

Salt formations are worldwide. The best-known European deposits are at Stassfurt, Germany; in Galicia, Poland; near Strasbourg, France; and in the Salzkammergut, Austrian Tyrol. In the U.S., halite is mined in New York State, Michigan, New Mexico, and Louisiana; it is obtained as brine in New York State, Kansas, and elsewhere. Good crystals form on the surface of evaporating dry lakes, as at Great Salt Lake, Utah, and in Death Valley, California. A short-lived pink coloration on halite crystals at Searles Lake, California, is due to an algae that grows in brine. Near Bogota, Colombia, a church has been hewn in a salt mine.

Halite (especially in the Stassfurt and New Mexico occurrences) sometimes shows an intense blue to violet color, which forms clouds and irregular patches. This is thought to be attributable to free sodium, or colloidal sodium, combined with natural irradiation and some heat of burial. When such a specimen is dissolved in water, the solution remains colorless, and so is any salt that may be recrystallized from such a brine. With subsequent heat, some irradiation experiments have been successful in creating blue halite, but lake-surface, Bonneville Flats halite crusts only turn black.

For the market widely known as "Halite", see Central Sofia Market Hall.

For BitTorrent client, see Halite (BitTorrent client).

Halite
General
Category	Halide mineral
Chemical formula	Sodium chloride NaCl
Identification
Color	colorless or white; also blue, purple, red, pink, yellow, orange, or gray
Crystal habit	predominantly cubes and in massive sedimentary beds, but also granular, fibrous and compact
Crystal system	isometric 4/m 3 2/m
Cleavage	Perfect {001}, three directions cubic
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	2 - 2.5
Luster	Vitreous
Streak	white
Diaphaneity	Transparent
Specific gravity	2.17
Optical properties	Isotropic
Refractive index	1.544
Solubility	in water
Other characteristics	Salty flavor, Fluorescent
References	[1]

Halite is the mineral form of sodium chloride, NaCl, commonly known as rock salt. 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 the amount and type of impurities. It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, and borates.

Contents 1 Occurrence 2 Uses 3 Gallery 4 See also 5 References

Occurrence

Halite occurs in vast beds of sedimentary evaporite minerals that result from the drying up of enclosed lakes, playas, and seas. Salt beds may be up to hundreds of meters thick and underlie broad areas. In the United States and Canada extensive underground beds extend from the Appalachian basin of western New York through parts of Ontario and under much of the Michigan Basin. Other deposits are in Ohio, Kansas, New Mexico, Nova Scotia and Saskatchewan.

Salt domes are vertical diapirs or pipe-like masses of salt that have been essentially "squeezed up" from underlying salt beds by mobilization due to the weight of overlying rock. Salt domes contain anhydrite, gypsum, and native sulfur, in addition to halite and sylvite. They are common along the Gulf coasts of Texas and Louisiana and are often associated with petroleum deposits. Germany, Spain, the Netherlands, Romania and Iran also have salt domes. Salt glaciers exist in arid Iran where the salt has broken through the surface at high elevation and flows downhill. In all of these cases, halite is said to be behaving in the manner of a rheid.

Hopper crystal cast of halite in a Jurassic rock, Carmel Formation, Utah.

Unusual, purple, fibrous vein filling halite is found in France and a few other localities. Halite crystals termed hopper crystals appear to be "skeletons" of the typical cubes, with the edges present and stairstep depressions on, or rather in, each crystal face. In a rapidly crystallizing environment the edges of the cubes simply grow faster than the centers. Halite crystals form very quickly in some rapidly evaporating lakes resulting in modern artefacts with a coating or encrustation of halite crystals. Halite flowers are rare stalactites of curling fibers of halite that are found in certain arid caves of Australia's Nullarbor Plain. Halite stalactites and encrustations are also reported in the Quincy native copper mine of Hancock, Michigan.

Uses

Halite is often used both residentially and municipally for managing ice. Because brine (a solution of water and salt) has a lower freezing point than ordinary water, putting salt on ice will cause it to melt. It is common for homeowners in cold climates to spread 'rock salt' on their walkways and sometimes driveways after a snow storm to melt the ice. It is not necessary to use so much salt that the ice is completely melted; rather, a small amount of salt will weaken the ice so that it can be easily removed by other means. Also, many cities will spread a mixture of sand and salt on roads during and after a snowstorm to improve traction.

Rock salt is also used to make ice cream. It is not actually used in the ice cream mixture; rather, it is used to melt the ice surrounding the can holding the ice cream, causing the ice to melt at a lower temperature, thus lowering the temperature of the ice bath and quickening the freezing process.

Rock salt is also occasionally used instead of a slug or shot in shotgun shells as a less-than-lethal option.

Gallery

Unusual halite crystals from Fayum, Egypt

Halite carved Salt Cathedral of Zipaquirá, Colombia

Large natural crystal of halite, showing cubic cleavage breaks

Yellow halite crystals

See also

• Edible salt
• Sodium chloride
• History of salt
• Winsford – rock salt mine in England
• Salt tectonics

References

Wikimedia Commons has media related to: Halite

1. ^ http://rruff.geo.arizona.edu/doclib/hom/halite.pdf Handbook of Mineralogy

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0-471-80580-7
• Anthony, John W; Bideaux, R.A.; Bladh, K.W.; Nicois, M.C., 1997, Handbook of Mineralogy: Halides, Hydroxides, Oxides, Mineral Data Publishing, Tucson ISBN 0-962-20972-4
• Mineral Galleries
• WebMineral
• Minerals.net
• Desert USA
• Halite stalactites

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