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When a group of historians were looking at the teeth of medieval skeletons for remnants of plant microremains, they discovered a bit of lapis luzuli wedged between the teeth of a 45 to 60-year-old woman who was buried at a monastery circa A.D. 997 to 1162. And that’s weird, considering how expensive lapis luzuli was at the time, and also that the amount of blue pigment wedged in those teeth suggests that whoever this woman was came into contact with the pigment on a daily basis.

NPR reports that the discovery might indicate that this woman produced illuminated manuscripts—and particularly luxurious ones, if she was using this blue ink. While the pigment could have theoretically gotten there by consuming it, being in close proximity to grinding it up, or from kissing the books (yep, these people made out with their books, particularly the images of Christ), all of those possibilities don’t quite make sense given the build-up of the pigment and the fact it was located behind the teeth. What seems more likely is that while moistening her brush in the bookmaking process, historians tell NPR, the pigment made its way to the back of her teeth.

At the time these manuscripts were painstakingly designed and constructed works of art made primarily by monks, though there have been several recorded examples of nuns making them such as Guda and Diemud, who made manuscripts in the 11th and 12th centuries, and Sibylla von Bondorf, who made manuscripts in the 15th century. But they are few and far between. In the study in Science Advances tracing the discovery of the pigment in this woman’s teeth, the researchers write that “even among books in women’s monastery libraries, fewer than 15% bear female names or titles, and before the 12th century, fewer than 1% of books can be attributed to women.”

So the next time historians come across an anonymously written illuminated manuscript, perhaps instead of assuming it’s a monk who penned it, they can now envision a dedicated old nun with extremely blue teeth!