Published by the American Geological Institute
Newsmagazine of the Earth Sciences
When a fine eye for art was not enough, museum curators and scientists sleuthed out the identity of ancient marble statues using oxygen isotopes. But comparing a work of art to its source rock was often hit or miss — few quarries have undergone the extensive fieldwork needed to provide a detailed understanding of the area.
Now, a doctoral student at the University of Georgia has completed the first systematic characterization of the Pentelic marble quarries on Mount Pentelikon in Greece, providing a geographically detailed isotopic database that will help source some of the world’s most prized Greek antiquities.
Increasing the resolution of the Pentelic database will have a tremendous effect on the field of marble studies, says Scott Pike, who spoke about his study at the Geological Society of America meeting in November. “Archeologists, art historians and museum curators may be able to probe further into questions concerning trade and commerce, development of aesthetic values and modern forgeries, ancient copies and disassociated fragments.”
In fact, Pike’s work has already helped to pinpoint the small group of quarries that supplied the source rock for the Elgin Marbles — sculptures that adorned the Parthenon as early as the fifth century B.C. Pike first mapped out all of the existing quarries in the ancient quarry region — studying a 500-meter wide and 1.2-kilometer long stretch up the south slope of Mount Pendeli. He then collected multiple marble samples from all the ancient quarries and analyzed the isotope ratios of carbon and oxygen in the calcite, the primary mineral in marble.
Pike noticed that three neighboring quarries in the upper section of the quarry area have marbles with very high oxygen-18 ratios when compared to samples from all of the other Pentelic quarries, ratios that correlate with the published values of the Elgin marbles. “The data not only confirms that the Elgin marbles are Pentelic, we can now pinpoint the exact quarries from which the marble was extracted,” he says.
His work has also helped document the unique isotopic differences among quarries found along what Norman Herz, the pioneer of the isotopic technique and now an professor emeritus of geology at Georgia, calls “one of the most important quarry sites in classical archeology.”
But isotopic analysis is not always a guarantee of a sculpture’s origin. A combination of expertise is needed to pinpoint a marble artifact’s origin. Sometimes it does take an expert with an eye for marble to tell the difference. Marble at Cape Vathy on the Greek Island of Thasos has an isotopic signature similar to the Pendeli marble, says John Herrmann, curator of ancient art at the Boston Museum of Fine Arts. The same signature is also found in marble from the island of Naxos. Identifying the different marbles comes down to grain size. Unlike the fine-grain marble of Pendeli, Thasos and Naxos sport coarse-grain marbles.