Archaeological evidence underlines the historical importance of what was highly expensive salt. For example, the 6,500-year-old city of Solnitsata (Bulgaria), is one of the earliest known walled settlements of Europe and was primarily built as a salt production facility use a brine spring source. Its inhabitants used boiling processes to 'bake' and package the salt in ready-to-trade blocks the town is believed to have traded throughout the Balkans. An extensive collection of gold objects nearby led archaeologists to speculate that the salt trade resulted in considerable wealth for the town's residents. The city is believed to have been destroyed by an earthquake.
Salted fish began to appear by the 3rd millennium BC in ancient China and Egypt, and the technology required drove more effective mummification methods in Egypt. The Egyptians and Chinese also began to trade salted fish by the 2nd millennium BC, while the Phoenician empire traded salt at huge profits across the Mediterranean, circa post 9th century BC.
In the second half of the 19th Century, industrial mining and new drilling techniques discovered more and deeper salt deposits possible, increasing mine salt's share of the market over pan production. Although mining salt was generally more expensive than extracting it from brine via solar evaporation of seawater, the introduction of this new source reduced the price of salt due to a reduction of monopolization. Finally, the end of the 19th Century heralded widespread use of refrigeration and the demise of salt as a high-value commodity. Today, most people think of salt in terms of sprinkling it on their food, and in colder climates, they may also think in terms of road de-icing. These are, in fact, lesser modern usages of halite; its main use today is as a primary feedstock to the chemical industry.