Rock salt is the common name of "halite," or the mineral form of sodium chloride. Rock salt is mined from underground deposits surrounding inland seas and dry lake beds. It differs from table salt, primarily in size. Large, chunky rock salt crystals have diverse uses. When deciding how much rock salt to use in a specific project, the density of this mineral is a significant measure, as well as the physical characteristics of deicing salt.
It's important to calculate density in any conversion between weights and volumes, because large objects may be light in weight and small objects may be heavy. The comparison between a ton of feathers and a ton of lead illustrates this principle. Density equals weight divided by volume.
The Salt Institute lists the density of rock salt at 2.165g/cm 3.
The Salt Institute says rock salt weighs 80 lbs. per cubic foot, or 2,160 lbs. per cubic yard. The formula is 80 times 27, divided by 2,000, which equals 1.08 tons. The institute uses the weight of 80 lbs. because the density can range from 72 lbs. per cubic ft loose to 84 lbs. per cubic foot compacted.
Deicing rock salt falls freely into a pile, with the sides always at a slope of 32 degrees. So a ton of salt would require 25 cubic feet of storage space.