Lapis lazuli
From Tardis Wiki, the free Doctor Who reference
Lapis lazuli was a bright blue material.
Ta-Nin wore a necklace of lapis lazuli. The tables in the feast hall of the palace of Uruk were inlaid with lapis lazuli. (PROSE: Timewyrm: Genesys [+]Loading...["Timewyrm: Genesys (novel)"])
The walls of Babylon were built of bricks the colour of lapis lazuli. (AUDIO: Farewell, Great Macedon [+]Loading...["Farewell, Great Macedon (audio story)"])