Choosing the Right Tool for the Job: Ancient Milling in Volubilis

Volubilis is an outstanding archaeological site in Morroco. It was founded in the 3rd century B.C..

The ruins of Volubilis, a city in Morocco that was part of the Roman Empire. Credit: Sergio Morchon/ Flickr

It became an important outpost of the Roman Empire and was graced with many fine buildings. Extensive remains of these survive in the archaeological site, located in a fertile agricultural area. Volubilis was later briefly to become the capital of Idris I, founder of the Idrisid dynasty, who is buried at nearby Moulay Idris.

A team of geoscientists and archaeologists at a University of Texas at Austin geology lab have been analysing the stone tools found at the site. Their research has revealed that dough mixing vats and millstones from Roman-era ruins of Volubilis were made from specific rock types that probably improved each tool’s function.  

An olive millstone in Volubilis. Research assistant Drew Messing holds a tool for scale. Credit Jared Benton

The researchers were also able to show that the stones were sourced locally, a discovery that challenges a theory that some millstones had been imported from afar. It also means that the craftspeople who made the tools may have received input directly from the workers who used them.  

Jared Benton, a study co-author and an assistant professor at Old Dominion University who studies trade between Roman-era workshops, explained:

“It is interesting because it is a very local source and seemingly from one source.

“One wonders if there’s not a group of bakers that are coming together and saying let’s buy our stuff from this one quarry, or maybe there’s just one guy who [sells the stones], and that’s it.”  

The researchers found that there was a rock type for each tool type. Grain millstones were made from vesicular basalts (a volcanic stone full of sharp-edged pores); olive mills were made from clastic, fossiliferous limestone (a limestone containing fragments of other rocks and small fossil shells); and dough mixers were made from limestone with no clastic material or fossils.   

Derek Weller, a postdoctoral researcher at the University of Tokyo’s Earthquake Research Institute who led the study, also used the geochemical data to determine that all the stones came from sources near Volubilis. 

Limestone is plentiful in the region, and two limestone quarries were already known to be active during the Roman era near Volubilis. But archaeologists previously thought the basalt – which Weller found came from the nearby Middle Atlas Mountains – was imported from Italy.  

In addition, the research found that each rock type came from a single location rather than sourced from different places around Volubilis. Jared Benton said this suggests that a single supplier for each stone type might have been meeting all demand in the city and getting input from local people.   

Lauren LoBue, an undergraduate student at the The Jackson School of Geosciences, prepping samples from the stone tools for study. Credit Phil Orlandini

Elizabeth Fentress, an archaeologist specializing in Roman settlements in North Africa, said that the study is a great example of collaborative research.  

“It is hardly the only collaboration between geologists and archaeologists, but an excellent one,” she said.

“The key is, as here, that the archaeologists ask the right questions and use their knowledge to interpret the answers.” 

Additional co-authors include Omero “Phil” Orlandini, research associate and manager of the Electron Microbeam Laboratory at the UT Jackson School of Geosciences; Lauren LoBue and Scott Culotta, both undergraduates at the Jackson School; and Christy Schirmer, a graduate student in UT’s Department of Classics.  

The results were published in the Journal of Archaeological Science: Reports. 

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