The mineral halite

Chemical Formula

NaCl

Composition

Sodium chloride

Color

Colorless, white, red, yellow, orange, pink, green, blue, violet, gray

Streak

White

Hardness

2 - 2½

Crystal Forms
and Aggregates

(Isometric) Crystals occur as cubes, often distorted with hopper growth. Rarely occurs in octahedrons. Normally occurs massive, grainy, and incrusting. Large cubic chunks often break apart into cubic cleavage fragments.

Transparency

Transparent to translucent

Specific Gravity

2.1 - 2.6

Luster

Vitreous

Cleavage

1,all sides - cubic

Fracture

Conchoidal

Tenacity

Brittle

Other ID Marks

1) Sharp salt taste
2) Soluble in water
3) Some specimens fluoresce, usually red

Other Names

Salt,

Common Salt,

Natural Salt

Varieties

Rock Salt - Rock Salt is at times referred to as Halite, but it is really a rock (not a mineral) composed of 95 to 99 percent Halite, containing impurities such as Anhydrite, Gypsum, Dolomite, Quartz, and Pyrite.

Hydrohalite - Hydrohalite is not a variety of Halite, but a very rare, similar mineral. Its formula is "NaCl · 2H₂O", which is in essence Halite containing water. It forms only under very unique conditions where the water does not dissolve the salt. When the salt in sea water or saline spring water in very cold climates crystallizes, it forms together with ice which has no dissolving effect on salt. The ice forms an integral part of the structure of the mineral, and causes the mineral to be stable.

In Group

Halides

All About

Halite is extremely common. It is found in solid masses, and as a dissolved solution in the oceans and many inland lakes. The inland lakes that are rich in salt exist in arid regions, and are commonly below sea level without an outlet. In many of them there is more water being evaporated than the amount coming in, causing a recede in the water level of the lake and an increase of salinity content. This has only recently become an issue, for much of the tributaries to the lakes have running water which is partially drained for human usage. As the water evaporates, chunks of salt are leftover on the shores of the lake. The water levels can be extremely high in salt content, and a stick or stone placed in the water will become coated with a layer of Halite if allowed to form. Many of these inland lakes have already dried up, leaving over enormous salt deposits which are commercially mined.

Halite also exists in non-arid regions. It is only possible for it to exist in underground deposits, for anything on the surface would dissolve from rainwater. Enormous deposits exist underground in certain areas, reaching great depths. These deposits are mined by drilling wells into the salt layer, and bringing in hot water which quickly dissolves the salt. The water becomes saturated with dissolved salt (the solution is known as "brine") and is then pumped out. The brine evaporates and the remainder is mostly salt, which is refined and then put to use. Hopper shaped cubes may result when the brine is evaporated.

In some underground salt deposits in Texas and Louisiana, the salt is pushed upwards by an underground force through soft ground and forms arched structures known as "salt domes".

Uses

Halite is the source of common salt. Enormous Halite deposits are worked for salt. Salt has many uses, and must be heavily mined to satisfy demand. Some of its most famous uses are:

as food seasoning

for road safety to melt snow and ice

as salt licks for cattle (these provide the cattle with salt, which is essential to their health)

for medicinal purposes.

Halite is also the most important ore of both sodium and chlorine.

Striking Features

Salty taste, softness, and crystal formations

Popularity (1-4)

Prevalence (1-3)

Demand (1-3)

Distinguishing
Similar Minerals

The powerful salt taste as well as the crystal formations distinguishes Halite from practically every mineral.

Commonly
Occurs With

Anhydrite, Gypsum, Dolomite, Thenardite, Glauberite, Borax, Kernite, Quartz, Pyrite, (Shale)

Noteworthy
Localities

Halite comes from numerous localities, and only the most prestigious will be mentioned here. Perfect cubes embedded on matrixes have come from Salzburg, Austria. Fine crystals also occur in Stassfurt, Hessen, Germany, and in Galicia, Poland. In the U.S., enormous underground deposits exist in certain parts of New York, Michigan, Ohio, Kansas, Oklahoma, Texas, and Louisiana. Fine crystals exist above ground only in arid regions, usually near dry or saline lakes. Many such areas exist, such as Searles Lake, San Bernardino Co., California; the dry lakes of Kern Co., California; Salton Sea, Riverside and Imperial Cos., California; Death Valley, Inyo Co., California; Lake Bonneville and the Great Salt Lake, Utah; and the Dead Sea, Israel.

Picture Icon
Links

Picture Links

1. Hopper Halite crystals
2. Mass of microcrystalline Halite
3. Colorless Halite
4. Halite encrusting a stick
5. Pink Halite