In his book , Mark Kurlansky explores how this seemingly simple mineral has been a cornerstone of human civilization for millennia. He details how salt—the "only rock we eat"—has influenced everything from global trade routes and the rise of empires to the etymology of everyday words. Core Themes & Historical Impact

: Salt was once so valuable it was used as currency; the Roman practice of paying soldiers in salt is the origin of the word "salary" and the expression "worth his salt".

: The quest for salt inspired early inventions, such as natural gas furnaces in ancient China and drilling techniques that eventually led to the petroleum age. Salt: A World History: Kurlansky, Mark - Books - Amazon.com