Current sectionArchaeologyResearchers devise method to determine whether ancient clay artifacts are authentic by analyzing the signal left over millennia by the ambient 'noise' of Earth's magnetic fieldShare to FacebookShare to XArticle printing is available to subscribers onlyPrint in a simple, ad-free formatSubscribeComments: Zen reading is available to subscribers onlyAd-free and in a comfortable reading formatSubscribeA vessel sold as a souvenir in Jerusalem known to be modern and an animal-shaped vessel which turned out to be authentic (with an illustration of a magnetic field in the background). Figure preparation: Yoav Vaknin and Lisa Tauxe. Credit: Yoav Vaknin and Lisa TauxeA vessel sold as a souvenir in Jerusalem known to be modern and an animal-shaped vessel which turned out to be authentic (with an illustration of a magnetic field in the background). Figure preparation: Yoav Vaknin and Lisa Tauxe. Credit: Yoav Vaknin and Lisa Tauxe10:00 PM • August 31 2026 IDTOur planet's magnetic field has many nifty uses, the main one being keeping us all alive by protecting us from cosmic radiation. Now researchers have found that geomagnetism can also help them suss out whether an ancient artifact is authentic or the work of a clever forger.The new method only works on fired clay artifacts, a team of geophysicists reported Monday in PNAS. It relies on the fact that simply by sitting for a long time in Earth's magnetic field, these objects acquire a residual magnetic signature, say the researchers, led by Dr. Yoav Vaknin and Prof. Lisa Tauxe at the University of California San Diego. In brief, the stronger this remnant magnetization is – the older the artifact is.Archaeologists greatly prefer when antiquities are unearthed in controlled excavations: that way there can be little doubt about their authenticity and a host of data may be collected from the context in which they were found. Sadly, museums and public collections are filled with ceramics whose provenance is unknown, as they were seized by authorities on the illegal antiquities market or came from longstanding private collections.Without context, archaeologists can't say much about the origin of these objects and often their very authenticity is fiercely debated, meaning they can't be used to glean insight on the periods in which they were ostensibly made.Yes, there are scientific tests that can be performed, but forgers have learned to fool those too, so they are not conclusive, Vaknin tells Haaretz. Hence the need for a new method.When pottery is fired in a kiln, or otherwise burned in a fire, tiny ferromagnetic particles in the clay act like small compass needles, recording the intensity and the direction of the Earth's magnetic field at the time the ceramic was last brought to a high temperature. This so-called Thermal Remanent Magnetization, or TRM, is invaluable to researchers who specialize in archaeomagnetism. It can provide precious data on how our planet's magnetic field, which fluctuates wildly for unclear reasons, looked in the past. It can also help date more precisely a specific artifact if researchers can correlate the magnetic signature to known paleomagnetic data. But this strong and very diagnostic magnetic signal is not what is used in the newly proposed authenticity test. Over the centuries, some of the minerals in the clay will continue to react with the ambient magnetic field, acquiring a weak signal that records a different intensity and direction of the field than the TRM, Vaknin explains. This Viscous Remnant Magnetization, or VRM, is a bit of a nuisance in most paleomagnetic experiments. Researchers treat it as noise and remove it by heating their sample in order to focus on the main magnetic signature, such as the TRM, Vaknin says. The VRM has been known since the late 19th century and researchers have already tried over the last decades to use it to date geological events, but because the signal is so weak the results are not particularly precise. Still, it is enough to help determine if an artifact is authentic."The resolution we require is not very high; we just want to know if an object is ancient or modern," Vaknin says.To test their proposed method, Vaknin and colleagues experimented on 45 clay items that were already known to be ancient or modern. They tested ancient storage jars from the Kingdom of Judah and pottery sherds unearthed in controlled excavations versus modern vessels, a group of fake seal impressions made especially for the study and souvenir pottery sold to tourists in Jerusalem. During the experiment the researchers heated a small sample from each vessel and checked at what temperature the VRM disappeared. Fake seal impression made by Rachel Pelta for this study Credit: Yoav Vaknin.Fake seal impression made by Rachel Pelta for this study Credit: Yoav Vaknin.They found that in modern vessels this magnetic signal disappeared at lower temperatures, whereas for the ancient ones it persisted until above 112 degrees Celsius (233 degrees Fahrenheit). So, as a rule of thumb, any clay artifact whose VRM is removed above this temperature can be safely assumed to be at least 1,000 years old, Vaknin and colleagues conclude. Of course this makes it hard to use the method to authenticate, say, medieval pottery, but at least the ancient period is covered. Plus, it is always possible that future research will be able to refine the measurements.As a first practical application of the method, the team also tested three artifacts that had been recovered on the illegal antiquities market by the Israel Antiquities Authority. These appeared to be artifacts from the Iron Age, which could make them up to 3,000 years old: a juglet that showed marks of being burned by a fire, an animal-shaped vessel probably used for cultic purposes, and an oil lamp. All three passed the test and are therefore seemingly authentic, the researchers report.This of course won't tell archaeologists where the artifacts were dug up or when exactly they were made but at least they know they are not forgeries. The new method offers investigators and researchers a new tool to authenticate disputed artifacts. This is always welcome because there is a constant race between scientists and forgers, in which the latter have an unfair advantage, Vaknin says."There is a problem in the authentication field: on one side are the scientists who publish their findings and on the other side are the forgers who do their work secretly," he says. "So it's hard for us to be ahead of the forgers since they can read our papers and figure out ways to trick our methods."Lior Bar-Sovik placing modern vessels which she made in a traditional kiln Credit: Lior Bar-SovikLior Bar-Sovik placing modern vessels which she made in a traditional kiln Credit: Lior Bar-SovikA vessel sold as a souvenir in Jerusalem known to be modern and an animal-shaped vessel which turned out to be authentic (with an illustration of a magnetic field in the background). Figure preparation: Yoav Vaknin and Lisa Tauxe. Credit: Yoav Vaknin and Lisa TauxeA vessel sold as a souvenir in Jerusalem known to be modern and an animal-shaped vessel which turned out to be authentic (with an illustration of a magnetic field in the background). Figure preparation: Yoav Vaknin and Lisa Tauxe. 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