Because there are so many different types and grades of salt, it’s always a good idea to have a basic notion of how rock salt originates.
Like gasoline and natural gas, rock salt is an important resource. The difference, of course, is that rock salt is available in huge amounts, and all levels of purity are useful for one industry or another. For example, although most rock salt is not edible, it is often used in culinary processes which do not require the salt as a direct ingredient.
Rock salt is also used to change the properties of water or other materials used in manufacturing, while the rock salt itself is not used in the final product.
Rock salt, also known as halite, is a very common mineral, with an interesting back story. Just as oil develops around natural deposits of vegetation, rock salt is often found where there was once an inland lake, which has dried up and been covered by hundreds or thousands of years of sedimentation and geological formations. These deposits tend to crystallize, and often contain minerals and impurities from the surrounding soil, much like petrified organic material.
For this reason, rock salt must undergo a purification process, or be separated from less pure forms before it may be consumed.
As indicated earlier, most rock salt is not directly consumed by humans or animals, but is used in indirect manufacturing processes, often changing the chemical properties of other materials. While some discoloration of salt is caused by mineral impurities, other colors are caused by the bending of light through the salt lattice. So, it is entirely possible that rock salt with an odd hue is actually a very pure form.
Sources for rock salt
Rock salt does not always form from ancient lakes. Other sources of salt are pushed up through the earth by volcanic forces, creating fascinating geological formations limited to unique areas. These are often mined in the same manner as more typical formations, creating underground chambers which are carefully engineered for controlled mining activities.
Everything from explosions to wells of hot water are used to bring rock salt to the surface, although the pillar and chamber technique is the most common. Since the source of rock salt often defines its grade, and therefore indicates the proper use for a type of rock salt, choosing a quality rock salt supplier is the next best thing to being an expert on rock salt itself.