Everything you need to understand or teach Salt by Mark Kurlansky.
Salt is the history of the world told from the point of view of the only rock that we eat, which is salt. The scope of this book is epic in that it starts at the beginning of recorded world history and ends at roughly present day times.
The first several chapters in the first section of the book deal with the procurement and use of salt in the ancient world...
Salt: A World History Lesson Plans contain 101 pages of teaching material, including: