Halite facts for kids
Quick facts for kids Halite |
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Halite from the Wieliczka salt mine, Małopolskie, Poland (size: 16x15x13cm)
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| General | |
| Category | Halide mineral |
| Formula (repeating unit) |
NaCl |
| Strunz classification | 03.AA.20 |
| Crystal symmetry | Isometric hexoctahedral 4/m 3 2/m |
| Unit cell | a = 5.6404(1) Å; Z = 4 |
| Identification | |
| Formula mass | 58.433 g/mol |
| 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 | Cubic |
| 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 | n = 1.544 |
| Solubility | Water soluble |
| Other characteristics | Salty flavor, Fluorescent |
Halite is a mineral that many people know as "rock salt." It's a natural form of sodium chloride (NaCl). This is the same chemical compound as the table salt you use for cooking! Halite often looks like it is made out of tiny cubes.
Contents
Where Halite is Found
Halite is found in huge layers deep underground. These layers are called sedimentary evaporite minerals. They form when large, enclosed lakes or seas dry up. As the water evaporates, the salt is left behind.
These salt beds can be hundreds of meters thick. They can cover very large areas. For example, in the United States and Canada, there are huge underground beds. They stretch from the Appalachian Mountains through parts of Ontario and under much of the Michigan Basin. Other big deposits are in places like Ohio, Kansas, and New Mexico.
One of the biggest salt deposits is the Khewra Salt Mines in Pakistan. In the United Kingdom, the largest mine is at Winsford in Cheshire. It produces about a million tons of salt each year.
Salt Domes
Sometimes, salt layers deep underground get squeezed upwards. This happens because of the weight of the rocks above them. These squeezed-up salt masses are called Salt domes. They look like vertical pipes or columns of salt.
Salt domes are common along the Gulf of Mexico coasts of Texas and Louisiana. They often have petroleum (oil) deposits nearby. Other countries like Germany and Iran also have salt domes. In very dry places like Iran, salt can even break through the ground and flow downhill like a slow glacier.
Unusual Halite Crystals
Some halite crystals look very unique. For example, purple, stringy halite can be found in France. There are also "hopper crystals." These look like hollow cubes with stair-step shapes on their faces. They form when salt crystallizes very quickly. The edges of the cube grow faster than the middle.
In some dry caves in Australia, you can find "halite flowers." These are rare stalactites made of curling salt fibers. They are quite beautiful and unusual.
How Halite is Used
Halite, or rock salt, has many important uses in our daily lives.
Melting Ice
One common use for halite is to melt ice. When salt is put on ice, it mixes with a thin layer of water on the ice's surface. This creates a salty water solution called brine. Brine freezes at a much lower temperature than pure water. This effect is called freezing-point depression.
So, if the temperature is near freezing (0°C or 32°F), adding salt will make the ice melt. People often spread salt on sidewalks and driveways after a snow storm. Cities also use a mix of sand and salt on roads. This helps to melt ice and improve traction for cars. You don't need a lot of salt to melt the ice completely. A small amount can weaken the ice, making it easier to remove.
In Food and Agriculture
Salt is also used a lot in cooking. It makes food taste better and helps to preserve many foods. Think of bacon or salted fish. You can grind larger pieces of rock salt in a salt mill or sprinkle it over food.
In some cultures, especially in Africa, people prefer different types of rock salts. They believe different colors of salt mean different flavors. This is because the colors come from tiny amounts of other minerals mixed in. Many traditional recipes even ask for specific kinds of rock salt.
Sometimes, rock salt is used in farming. For example, it can be used to stop certain unwanted grasses from growing in fields.
Gallery
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Sharp halite crystals that have this green color from inclusions of malachite
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Large natural crystal of halite, showing cubic cleavage breaks
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Pink color halite on a matrix covered with minute nahcolite
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Halite from Potash Corporation of Saskatchewan Mine in Rocanville, Saskatchewan, Canada
Images for kids
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Halite Bore sample, Laos
See also
In Spanish: Halita para niños
