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Lava Flows and Vesicular Basalts
Some newly erupted lava flows contain abundant dissolved gas. The gas bubbles in the flow move upwards towards the surface in an attempt to escape while the lava is still molten. However, once the lava starts to solidify, the bubbles are trapped in the rock. These trapped gas bubbles are known as vesicles. If the upper portion…
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Cinder Cones
Most of the scoria falls to the ground near the vent to build up a cone-shaped hill called a “cinder cone.” Cinder cones are generally small volcanoes produced by brief eruptions with a total vertical relief of less than a few thousand feet. They are usually very steep because scoria has an angle of repose…
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How Does Scoria Form?
Scoria forms when magma containing abundant dissolved gas flows from a volcano or is blown out during an eruption. As the molten rock emerges from the Earth, the pressure upon it is reduced and the dissolved gas starts to escape in the form of bubbles. If the molten rock solidifies before the gas has escaped,…
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What is Scoria?
Scoria is a dark-colored igneous rock with abundant round bubble-like cavities known as vesicles. It ranges in color from black or dark gray to deep reddish brown. Scoria usually has a composition similar to basalt, but it can also have a composition similar to andesite. Many people believe that small pieces of scoria look like the ash produced in a…
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Uses of Rock Salt
Rock salt has many uses. The most important uses in the United States are described below. Highway Deicing The leading use of rock salt in the United States is highway deicing. In calendar year 2020, an estimated 43% of rock salt consumption was used for this purpose. The amount of highway salt consumed varies significantly…
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Rock Salt Producers
The United States Geological Survey Mineral Commodity Summaries for 2021 reports that “almost every country in the world has salt deposits or solar evaporation operations of various sizes”. Eight countries (China, the United States, India, Germany, Australia, Canada, Chile, and Mexico) each produced at least 9 million tons of salt in calendar year 2020. The accompanying pie chart illustrates their relative importance. Much of…
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Solar Salt
People have been producing solar salt from ocean water for thousands of years. Solar salt can be produced in parts of the world where evaporation rates significantly exceed precipitation rates. The name “solar” means that the sun acts as a heat source to evaporate ocean water (or brine brought up from the subsurface), leaving behind…
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Vacuum Pan Salt
Vacuum pan salt is produced in large enclosed tanks known as vacuum pans or vacuum salt crystallizers. The tanks are filled with brine, which is heated by injecting steam into the tank. The steam heats the brine and causes it to boil. As the brine boils it produces additional steam, which is fed into a…
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Solution Mining
Solution mining of salt is done by injecting hot water under pressure down a well into a subsurface layer of rock salt. That same water is then withdrawn up to the surface through a nearby recovery well. While the water travels through the layer of rock salt – from the injection well to the recovery…
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Underground Mining
Companies interested in developing a salt resource located hundreds to thousands of feet below the surface usually drill numerous wells down to and through the salt layer. They drill to learn the thickness of the salt and what types of rocks enclose it. They also obtain core samples of the salt (see accompanying photo) that…