Salt: A Unique Mineral and Great Teaching Tool

Salt is a common mineral found worldwide called halite. Many people also call the mineral rock salt. The mineral is very soft in relation to other minerals and can form nice crystal shapes. The crystals can forms individually in crystalline masses. Rock salt forms as a common sedimentary deposit in areas of enclosed salt water. Salt is a versatile teaching tool because it has definite physical properties that are easy to recognize and you can perform in class and at home experiments as a demonstration.

What is Salt?

Rock salt is composed of the mineral halite, which gets its name from the Greek word for salt. Halite has the chemical formula NaCl, or sodium chloride. Samples are typically white to clear in color but can also be blue, pink, yellow, red and purple. A soft mineral, halite is only a two and one half of the Mohs Hardness Scale and is easily scratched by a penny or paperclip. Most salt crystals are white in color but can also be clear, yellow, pink, red, blue and purple. Halite forms good crystals with cubic cleavage and may forms as a mass of interwoven cubes in a singles deposit. The crystals have a glassy luster and a salty taste. Halite tastes salty!

Salt / Halite Formation and Locales

Halite forms from evaporation in beds. These beds are large areas that formerly contained salt water such as lakes or enclosed seawater. As the water evaporates, the salt precipitates out of solution forming layers of salt crystals. This photo is of the huge Salar de Uyuni Salt Flat in Bolivia. Evaporite beds may stay at the land surface or other rock layers may bury them over time. Buried salt beds may form underground salt domes over time. The salt beds are very malleable and lighter than most of the surrounding rocks. When a crack is present in the rock above a salt bed, the layer of salt will rise through the crack forming dome shape below ground.

Halite occurs in deposits worldwide. Some of the most notable locations are Antarctica, South America, Africa, Australia, Russia, Japan, China, Poland, Iran, Switzerland, Germany, UK, Ireland, Finland, Poland, Morocco and Canada. In the United States, thick rock salt beds are located in New York State and extend through Ontairo, Canada and into the Michigan Basin. Large deposits are also present in the Salina Formation beneath Cleveland, Ohio, and at locations in California, Arizona and New Mexico. Salt domes are commonly associated with oil deposits in the regions along the Gulf Coast of Louisiana and Texas as well as areas of Germany, Spain and Iran among others.

Uses for Halite / Salt

Halite is has many uses and is important to the chemical industry. The sodium and chloride in the rock salt are sources for the production of hydrochloric acid, chlorine, soaps, caustic soda, sodium hydroxide and ceramic glazes among other materials. Salt is also use as a seasoning in food for humans and animals. Rock salt is a good preservative for food and animal hides and is used to melt ice from roadways in the winter.

Teaching Geology with Salt

Salt is a great teaching tool to help children understand the properties of minerals and how to identify a sample. You can also do hands-on experiments to show children how salt crystals form from a solution. You can learn how to grow salt crystals in this fun blog article. Another fun experiment to do show kids is that halite forms cube shapes and has good cubic cleavage that means that you can hit salt with a hammer and it will break into smaller cubes. Classrooms and homeschool can use halite samples from mineral kits, such as the kits from Mini Me Geology.

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