They couldn't figure out the blue. Scientists studying tartar from the teeth of medieval skeletons hoped to learn a thing or two of about diets of the Middle Ages. But when they put the teeth and jaw of one woman under a microscope, they were surprised to see hundreds of tiny flecks of blue, reports the BBC. After much sleuthing, they figured out that the blue came from lapis lazuli, a rare and expensive stone ground into powder to make dye for sacred manuscripts. Typically, male monks have gotten most of the credit for working on such texts, but the amount of lapis lazuli in the woman's mouth suggests that she—and presumably other women—were also on the job. Researchers' best guess is that the blue flecks ended up in her teeth because she kept putting the tip of her brush in her mouth, reports the AP.
"It's kind of a bombshell for my field—it's so rare to find material evidence of women's artistic and literary work in the Middle Ages," says Alison Beach of Ohio State University, a professor of medieval history and co-author of the report in Science Advances. Another possibility is that the woman breathed in the lapis lazuli, known as ultramarine in its powder form, while preparing it for someone else, notes the Atlantic. The woman was found buried beneath an ancient cemetery in Germany and was likely a nun, say researchers. She lived between 997 and 1162AD and probably died around age 60. "For a medieval historian, this kind of clear material evidence of something from the life of an individual person is so extraordinary," says Beach. (Read more discoveries stories.)