via npr
“...These days you can walk into any drugstore and buy a cheap pack of markers in all the colors of the rainbow. That makes it hard to appreciate just how rare and precious blue pigment was, not so long ago.
“The translation of sacre bleu is sacred blue,” says [Christopher] Moore. “In medieval times, the church said that if you are going to portray the Virgin Mary's cloak, it has to be in a certain shade of blue. And that blue must be ultramarine, because ultramarine blue is permanent. It doesn't go black or fade as organic colors do. And that is made essentially from crushed lapis lazuli, which is only available in Afghanistan. If you think about the 11th and 12th century, trying to get a stone from Afghanistan to Europe, for years and right up into the 19th century, was more valuable, weight for weight, than gold…”
Read more about Christopher Moore's novel here.