Rock Salt
Rock Salt
Rock salt is an evaporate crystal which is typically colorless or white, but may also be other mixed colors depending on the amount and type of impurities. It commonly occurs with other evaporate deposit minerals such as several of the sulfates, halides, and borates.
Where's the salt?
Rock salt occurs in vast beds of sedimentary evaporate minerals that result from the drying up of ancient enclosed seas. Salt beds may be hundreds of feet thick across broad areas. In the United States and Canada, extensive underground beds extend from western New York through parts of Ontario and under much of the Michigan Basin.
How rock salt is used
Salt is one of the most popular methods of deicing roadways because of its ease of use, effectiveness, and relatively low cost compared to alternative de-icing methods. Salt brine has a lower freezing point than pure water, so putting salt on ice that is near freezing point will cause it to melt.