These blocks of salt bound with straw, and called 'amole tchew' (??? ??), were collected in Ethiopia by Major Powell-Cotton while hunting and exploring the country in 1899.
Salt has been mined from the chain of salt lakes in the Danakil or Afar Depression for hundreds of years. An Egyptian traveller in the 6th century first made reference to it but it is probably much, much older.
Salt is one of humankind's oldest raw materials. It is distributed unevenly throughout the world and yet it is an essential requirement for survival of all animal life, although in small quantities. These factors have given salt a great value, and even at times a religious significance.
Since medieval times coinage had not been in common use in Ethiopia. Gold measured by weight was employed by the merchants for large-scale transactions, but most people made use of barter, or so-called "primitive money" - things used for exchange purposes instead of money. Salt blocks were one example of these.