What is Halite?
• Chemistry: NaCl, Sodium Chloride
• Class: Halides
• Uses: Major source of salt and as
mineral specimens.
Halite, better known as rock salt, can
easily be distinguished by its taste.
Since taste is an important property of
salt, there is a right way to taste a
specimen of halite (or an unknown
mineral that is similar to halite) and a
wrong way. The right way is to first
lick your index finger, rub it against
the specimen and then taste the finger.
This limits the amount of the mineral
that actually gets in your mouth, an
important consideration when you
consider that there are poisonous
minerals that resemble halite.
Halite is found in many current
evaporative deposits. It is also found
in ancient bedrock all over the world
where large extinct salt lakes and seas
have evaporated millions of years ago,
leaving thick deposits of salt behind.
Perfectly formed cubes of halite are
typical of the habit of this mineral.
However it does form some unusual
interesting habits that are much sought
after by collectors. One habit is called
a hopper crystal which forms what has
been termed a skeleton of a crystal.
Just the edges of a hopper crystal
extend outward from the center of the
crystal leaving hollow stair step faces
between these edges. Hopper crystals
form due to the disparity of growth
rates between the crystal edges and the
crystal faces.
Often specimens are brightly colored
purple and blue and with the silky
luster due to the fibers, they represent
a wonderful and a very uncharacteristic
variety of halide. These specimens are a
must have for teachers of mineral
identification classes that want a
stumper for those end of the session ID
exams. Of course they are still easy to
identify with the oft forgot simple
taste test.
Well crystallized specimens of halite
cubes can be very impressive and
popular. Some are colored an attractive
pastel pink by inclusions of bacterial
debris that are trapped during
crystallization in an evaporative lake.
Often these specimens that are sold
world wide in rock shops and in mineral
shows where grown within the past year.
In fact, the crystals form so fast and
so well in some evaporative lakes that
mineral dealers are using their
imaginations to enhance their inventory.
They are putting sticks, animal skulls
and other imaginative items into these
lakes and retrieving them a relatively
short time later covered in clusters of
white or pink halite cubes.
Halite is a soft mineral that flows
easily under pressure. At depths of as
little as 3 kilometers, it begins to
rise through the rocks above it in
cylindrical plugs called salt domes.
These are of interest to oil prospectors
because petroleum collects around them.
Halite History & General Information
Halite (sodium chloride) comes from
the Greek halos, meaning "salt" and
lithos meaning "rock," and is in fact,
better known as rock salt. Halite is
called evaporate because it is formed by
the evaporation of saline water in
partially enclosed basins. It is very
common worldwide, deposited in solid
underground masses, and as a dissolved
solution in oceans and many arid-region
inland lakes.
Huge Halite deposits are mined for
common table salt (NaCl), which is in
great demand and has many uses,
including:
• food seasoning
• for road safety in the winter months
to melt snow and ice
• as salt licks for cattle to provide
them with essential salt
• for water softeners
• for medicinal purposes
• primary ore for both sodium and
chlorine
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.
Halite is mined by shaft mining or by
pumping water into the deposit and later
pumping out the brine. In purification,
potassium, and magnesium salts, bromine,
and iodine are obtained as by-products.
The halite is recrystallized, becoming
very pure in the process. In addition to
its use in food and as a preservative,
salt is essential in chemical
industries, in the manufacture of soda
ash for glass products, and in soap
making and metallurgy. Chlorine from
salt is used as bleach and in water
purification.
Underground Halite
When halite occurs in non-arid
regions, it is only possible for it to
exist in underground deposits, for
anything on the surface would dissolve
from rainwater. Indeed, a great deal of
halite is found in ancient bedrock all
over the world where large extinct salt
lakes and seas evaporated millions of
years ago, leaving behind thick deposits
of salt in beds that range from a few
feet to more than 1,000 feet in
thickness.
These deposits are mined by drilling
wells into the salt layer, and pumping
hot water to quickly dissolve the salt.
When the water becomes saturated with
dissolved salt (the solution is known as
"brine"), it is pumped out. When the
brine evaporates, the remainder is
primarily sodium chloride, which is
refined and utilized.
Aboveground Halite
Inland lakes that are rich in salt
exist in many arid regions, especially
in the Deserts. They usually have no
outlet, and are often below sea level.
In such lakes there is more water being
evaporated than the amount entering,
causing the volume of water to decrease,
while increasing its salinity.
In some lakes, concentrations of salt
brine can become so extreme that a stick
or stone placed in the water will become
coated with a layer of Halite. As the
water evaporates, the shoreline recedes
and chunks of salt are left crystallized
on the beaches. Many of these inland
lakes have already dried up completely,
leaving enormous salt deposits that are
commercially mined.
Halite Collection
Well crystallized specimens of halite
cubes are very impressive and quite
popular with rockhounds. Halite crystals
form so fast and so well in some
evaporative lakes that many such
specimens that are sold worldwide in
rock shops and at mineral shows were
grown within the past year
Some halite crystals are colored pinkish
by bacterial debris trapped during
crystallization while others are colored
bright purple or blue, with a silky
luster. Halite also forms some unusual
variations that are prized by
collectors. One variation, called a
hopper crystal, forms what has been
termed a skeleton of a crystal. Just the
edges of a hopper crystal extend outward
from the center; leaving hollow stair
step faces between these edges. Hopper
crystals form due to the disparity of
growth rates between the crystal edges
and the crystal faces.
Since taste is an important property of
salt, taste is one of the important
means of identifying this mineral. The
correct way to taste a mineral specimen
is to first lick your index finger, rub
it against the specimen and then taste
the finger. Remember that there are
poisonous minerals that resemble halite.
Hydro halite is not strictly a variety
of Halite, but a very rare, similar
mineral with the formula NaCl + 2H2O.
This variation forms only under very
unique conditions where the water does
not dissolve the salt and becomes an
integral part of the structure of the
mineral.
halite Physical Properties
Hardness |
2 |
Specific gravity |
2.1+ (light) |
Cleavage |
Perfect in three directions
forming cubes. |
Color |
Clear or white but can be found blue, purple, pink, yellow and gray. |
Fracture |
Conchoida |
Crystal Habits |
Predominantly
cubes and in massive sedimentary
beds, but also granular, fibrous
and compact. Some crystals show
a crystal type called a hopper
crystal described above. |
Luster |
Vitreous |
Streak |
White. |
Transparency crystals |
Crystals are transparent to translucent |
Crystal System |
Isometric; 4/m bar 3 2/m |
Characteristics |
Salty taste |
Associated |
Minerals include
Other evaporate deposit minerals
such as several sulfates,
halides and borates. |
Best Field Indicators |
Taste, cleavage and crystal habit |
Halite Chemical Properties of 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 |
|
Halite Usage
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 chemical purposes
• Halite is also the most important ore
of both sodium and chlorine.
Recommended Filled of Application
Kind of powder |
Talc |
Mica |
Kaolin |
Red Iron oxide |
Fluorine |
Dolomite |
Calcite |
Bentonite |
Barite |
Ceramics |
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Excavation |
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Elecrode |
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Paint |
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Plastic |
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