‘Ultramarine blue is a colour illustrious, beautiful, and most perfect, beyond all other colours’, wrote the Italian artist Cennino Cennini in the late 14th century. He and his contemporaries adored this mineral pigment for its rich, deep lustre. But they didn’t use it much, at least not unless they had a particularly wealthy client, because it was very costly. As the name implies, it came from ‘over the seas’ – all the way from what is now Afghanistan, where mines in the remote region of Badakhshan were the only known source of the parent mineral, lapis lazuli, for centuries. Not only was ultramarine expensive to import, but it was laborious to make: repeatedly grinding and washing the raw material to separate the blue colourant. Ultramarine could cost more than its weight in gold, and so painters reserved it for the most precious parts of their altarpieces, especially the robes of the Virgin Mary.  More…