Part of the reason we are named Deep Blue
A BLUE MORE EXPENSIVE THAN GOLD Ultramarine blue was a marker of social status. Mined in northeastern Afghanistan in the 14th and 15th centuries, it had to be brought down from the mountains on the backs of donkeys, then transported by ship to its final destination. It was so hard to get ahold of that it became incredibly expensive–even costlier than gold. Khandekar says that people who wanted to show off their piety (and maybe also their deep pockets) would request its use on altarpieces; the color was so expensive that it had to be a separate line item on the bill for the painting.
To extend their stores of the valuable pigment, artists would sometimes paint the Virgin’s mantle with azurite, a cheaper substance, and then cover it with a very thin layer of ultramarine. Others would mix in azurite or blue glass to extend their stores–and hope patrons with a discerning eye wouldn’t notice. The ultramarine market finally crashed in 1826, when a chemist discovered a synthetic version, making the brilliant blue color much more widely available.