Clean and Dirty Salt
Posted: May 1, 2017
What is salt, anyway?
Can you answer that question without pointing to a saltshaker?
Here’s the short answer. Salt is a mineral—something solid that has never been alive and people didn’t make. It’s made up of two chemicals: sodium and chloride. Before it gets refined for the dinner table, salt is called rock salt or halite.
Salt mines are formed over thousands of years while Earth’s plates slowly move. The plates cover up ancient, underground seabeds full of salt. Salt gotten from mines like this is too impure to use on food. But it works just fine for slippery roads.
How do people get clean salt? They have two ways. One is called solution mining. Workers dig wells above underground salt caverns. Then they draw up the salty water from the wells. After that, they boil the water away and take out any extra minerals mixed with the salt.
People also harvest salt straight from the ocean or from very salty lakes. They rely on the sun and wind for their work. The wind and sun evaporate the water from shallow pools. The salt stays behind. When the salt gets thick—usually once a year—people or machines gather it up. Then they wash, drain, and clean it. Solar evaporation only works in places like Australia, where very little rain falls and the sun is hot.