About 900 years ago, a woman living in a small religious community in Germany may have helped create one of the medieval world’s most luxurious objects: an illuminated manuscript.

Researchers examining her calcified dental plaque discovered more than 100 microscopic particles of blue pigment. Chemical analysis identified them as lapis lazuli, the semiprecious stone used to make ultramarine.

The finest lapis lazuli reached medieval Europe through trading networks extending toward mines in what is now Afghanistan. Its brilliant blue pigment was costly enough to be reserved for important manuscripts, often appearing beside gold and silver in decorated initials, borders and religious scenes.

The woman lived at Dalheim sometime between AD 997 and 1162. Its exact manuscript disappeared along with the monastery’s books, but it was probably a religious volume made for worship. One intriguing possibility is a liturgical book like the illuminated matutinal commissioned from a nearby women’s monastery during the same period. Such a book contained texts used during Matins, part of the daily cycle of monastic prayer.

The blue particles appeared throughout plaque from different teeth, suggesting repeated exposure. Researchers think she may have placed a fine paintbrush between her lips to shape its point while working. She might also have breathed pigment dust while grinding or preparing the color.

Either activity required access to an exceptionally valuable material and places her within the skilled production of luxury books. Medieval scribes and painters rarely signed their work, making women’s contributions particularly difficult to trace.

Dalheim’s manuscripts and records were eventually lost. Its possible artist left no written signature. The blue supplied one centuries later.

Source: A. Radini and colleagues, “Medieval women’s early involvement in manuscript production suggested by lapis lazuli identification in dental calculus,” Science Advances.