The earliest life on Earth might have been just as purple as it is green today, according to the “Purple Earth Hypothesis” proposed by a microbial geneticist in 2007. Therefore, you can imagine my curiosity when I discovered two vials labelled “purple earth” while researching the Forbes Pigment Collection at the Harvard Art Museums. I wondered what is this purple earth and where did it come from? Did it have any relation to the origins of the color purple? The search for the origin of the purple fragments led me on an unexpected journey to an ancient Greek pottery studio in Athens and excavations by a pioneer in the field of archaeology, Dr. Marie Farnsworth.
Provenance of the “Purple Earth” Pigments
Searching in the Harvard Art Museums’ Archives, I discovered that the pigments were donated in 1939 by a Dr. Marie Farnsworth, as part of a set of eight ancient Greek pigments dating back to the 5th century BC and discovered in the excavation of an ancient Athenian Potter’s studio at Agora of Athens.
With some more digging, I discovered that Dr. Marie Farnsworth was one of the first practitioners of archaeological chemistry and is accredited for decoding the formulas of ceramic glazes and pigments used during the Athens’ golden era. The application of chemistry within archaeology is important as it allows scientist to answer questions about what artifacts are made of, where they came from and how they have been changed through burial in the ground. Farnsworth’s started her career in archaeology as a research chemist at the Fogg Art Museum in the Department of Technical Research from 1936-1938. This Department of Technical Research—later renamed the Straus Center for Conservation and Technical Studies— was the first laboratory for art established in the United States and a vital training ground for pioneers that explored the intersections of art and science, attuned to the materials of art and the eﬀects of environment.
Agora Excavations at Athens
After her time at the Harvard Art Museums, Farnsworth joined the Agora Excavations in Athens in 1938 as a chemist to study ancient Greek pottery. The Ancient Agora of Athens is one of the best-known examples of an ancient Greek forum still in existence today. The excavations in the Athenian Agora began in 1931 by the American School of Classical Studies at Athens and continues to today.
According to Dr. Farnsworth field notes, the pigments were discovered in what is believed to be an ancient Greek potter’s studio during excavation of the retaining wall behind Stoa of Zeus Eleutherios, located in section 3 in the restored drawing of the Agora above. This cult of Zeus was established after the battle of Plataia in 479 B.C., when the Greeks drove the Persians out of Greece. It was unusual for a religious building to take the form of a stoa rather than a temple. Considering its central location, archaeologists believe that it is likely that the Stoa of Zeus Eleutherios also served other civic purposes.
According to the Athenian Agora fieldnotes from 1937, archaeologist discovered remnants of a pottery studio while excavating “filling behind retaining wall of Stoa of Zeus. The remains of unfired clay adhering to the interior of various pieces make it probable that the material in this filling is a mass of debris from the floor of a pottery works destroyed by subsequent building.” Researching the archives of the excavations in the Athenian Agora, I discovered a 1937 article in Hesperia : Journal of the American School of Classical Studies at Athens in which contained detailed illustrations of the pit in which the fragments of purple earth were excavated:
Images: “Exploratory pit behind retaining wall of the Stoa of Zeus.” Hesperia : Journal of the American School of Classical Studies at Athens. 6 (1937), p. 19-20, fig. 10 & 11. American School of Classical Studies at Athens.
In Farnsworth’s analysis and description of the pigments labelled “purple earth” , she stated:
2-25-35. A. Box 257: Purple Earth I. Dated to 3rd quarter of 5th century BC. Discovered in pit behind the retaining wall of Stoa, in Layer II of Purple Earth, within the Potter’s shop. Analysis reveals that it consists of Caley Fe2O3, CaCO3, clay, and sand. Possibly includes iron oxide and mortar, but not plaster.
2-25-35. A. Box 257: Purple Earth II. Dated to 3rd quarter of 5th century BC. Discovered in pit behind the retaining wall of Stoa, in Layer I of Purple Earth, within the Potter’s Shop
During her career, Dr. Farnsworth also identified the composition of Athenian cement as beeswax and lime, was the first to identify Hellenistic pink pigments as rose madder, and studied clay sources of Corinthian ware to determine the origin of Greek pottery. In 1980, she received the Pomerance Award for Scientific Contribution to Archaeology to honor her achievements.
Excavations of the Athenian Agora continue to this day. Although the purple earth may not lead to discoveries about the origins of life, the rich history of Athens and the ancient world uncovered by generations of archaeologists and scientist like Farnsworth are available on the Athena Agora Excavations website. The Farnsworth’s pigments reside at the Harvard Art Museums as one of over 2500 pigments in their Forbes pigment collection still being used today to enrich the understanding of and care for works of art.
 Harvard Art Museums Archives. Forbes, Edward Waldo, 1873-1969. Papers, 1867-2005. Box 22, Folder: 534, Duell, Prentice [1933-1958], (3of4).