From Scientific American:
According to Count Gleichen in “Mission to Menelik,” the people of Abyssinia use the Maria Theresa 1780 dollar. But for small change a very different coin is used: a bar of hard , crystallized salt, about ten inches long, slightly tapering toward the end. Five of these bars go for a dollar.
People are very particular about the standard of fineness of the currency. If it does not ring like metal when struck with the finger-nail, or if it is cracked or chipped, they will not take it. It is a token of affection when friends meet to give each other a lick of their respective amolis (bars), and in this way the value of the bar is decreased.
Yummy. Makes you feel a little silly about balking at sharing straws…