The Road to Oz (Unabridged‪)‬

The Emerald City is built all of beautiful marbles in which are set a profusion of emeralds, every one exquisitely cut and of very great size. There are other jewels used in the decorations inside the houses and palaces, such as rubies, diamonds, sapphires, amethysts and turquoises. But in the streets and upon the outside of the buildings only emeralds appear, from which circumstance the place is named the Emerald City of Oz.