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Rock Salt Production
In 2020 about 39 million tons of salt were produced in the United States. There are four important categories of rock salt production: The United States consumes more salt than it produces. To satisfy demand in 2020, about 16 million tons of salt were imported. The amount of imported salt has been increasing in the…
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Specialty Salts in Cooking
If you visit a store where cooking supplies and spices are sold, you might see salt in a wide variety of colors and textures being sold. Many of these “specialty salts” are natural materials. Others have been crystallized by people or processed to make a distinctive product. Salt is sometimes crystallized to produce flake-shaped grains…
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What Color Is Rock Salt?
Pure rock salt under bright illumination will range in color between colorless and white. Colorless salt is usually the most pure because the most common cause of color is impurities. White salt often contains minute gas-filled or fluid-filled cavities. Specimens or zones of other colors can be caused by mineral grains included in the salt,…
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How Does Rock Salt Form?
Deposits of rock salt thick enough for underground mining or solution mining form under a rare set of geological conditions. The deposits shown on the accompanying map formed during times of high sea level, when shallow seas spread over extensive areas of continental crust. To deposit a thick layer of salt, long periods of sea…
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What is Rock Salt?
Rock salt is the name of a sedimentary rock that consists almost entirely of halite, a mineral composed of sodium chloride, NaCl. It forms where large volumes of sea water or salty lake water evaporate from an arid-climate basin — where there is a replenishing flow of salt water and a restricted input of other water. Deposits of rock salt occur…
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Uses of Limestone
Limestone is a rock with a diversity of uses. It could be the one rock that is used in more ways than any other. Most limestone is made into crushed stone that is used in road base, railroad ballast, foundation stone, drainfields, concrete aggregate, and other construction uses. It is fired in a kiln with crushed shale to…
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Types of Limestone
There are many different types of limestone – each with its own name. These names are often based upon how the rock formed, its appearance, its composition, or its physical properties. Here are some of the more commonly encountered types of limestone. Chalk Chalk is the name of a limestone that forms from an accumulation of…
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Composition of Limestone
Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, or clay minerals delivered to the site by streams, currents and wave action. Particles of chert, pyrite, siderite, and other minerals…
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Evaporative (Cave) Limestones
Limestone can also form through evaporation. Stalactites, stalagmites, and other cave formations (often called “speleothems”) are examples of limestone that formed through evaporation. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave…
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Limestone-Forming Environments
Many limestone-forming environments are active on Earth today. Most of them are found in shallow parts of the ocean between 30 degrees north latitude and 30 degrees south latitude. Limestone is forming in the Caribbean Sea, Indian Ocean, Persian Gulf, Gulf of Mexico, around Pacific Ocean islands, and within the Indonesian archipelago. One of these areas is…