Researchers have discovered 50 rare cave pearls, some of which contain ancient Greek artifacts from the Hellenistic era, in an underground water system near Jerusalem. This is the first known instance of cave pearls containing man-made objects. The finding, recently published in Archaeometry, offers a unique window into life thousands of years ago.
The discovery took place in the Ain Joweizeh spring tunnel, a 232-meter-long water system believed to have been built between 900 BCE and 586 BCE. Located southwest of Jerusalem’s Old City, the tunnel is one of the longest in the region and was likely part of a royal estate.
What are cave pearls?
Cave pearls, round formations resembling pearls, are created when minerals build up around particles like sand grains. These formations require specific conditions to develop: mineral-rich water, water movement, and time.
Unlike most mineral formations that can take thousands of years to form, cave pearls can develop within a few hundred years.
The cave pearls were found in a section of the tunnel carved directly into the bedrock. Researchers identified pottery shards and bits of plaster encapsulated in 16 of the 50 pearls.
Artifacts from the ancient Greek and Byzantine era
The artifacts span several historical periods, including the Hellenistic (333–63 BCE), Roman (63 BCE–324 CE), and Byzantine (330–636 CE) eras. Some fragments date back even further, to the Middle Bronze Age II (around the 17th century BCE).
Dr. Azriel Yechezkel, a lead researcher, noted the significance of the find. “Our initial research focused on mapping and surveying for archaeological artifacts within the spring tunnel. Cave pearls, a rare type of speleothem, were not the primary objective of our investigation.”
He further added, “The discovery of these formations, and even more surprisingly, the presence of archaeological remains like pottery shards within them, was an unexpected and significant find.”
Notable discovery of cobalt-blue pottery
One notable discovery was pottery with a cobalt-blue glaze, a type of ceramic produced in places like Cyprus and Ephesus during the Hellenistic period. Experts believe an imported lamp with this glaze may have belonged to an engineer who worked on constructing or maintaining the tunnel.
The Ain Joweizeh tunnel shows evidence of repeated use and repairs over the centuries. The tunnel’s structure includes sections built with stone blocks and covered with stone slabs, while other parts are cut directly into the rock. Water from the spring tunnel flows northwest into a dry riverbed, eventually reaching the Refa’im stream.
Formation of the cave pearls
Researchers believe the formation of these cave pearls began during the Hellenistic period. The constant flow of water in the tunnel likely caused the tiny particles within the pearls to roll, forming smooth, round shapes. The discovery also provides insights into how the water flow and environment in the tunnel changed over time.
The tunnel remained active through the Roman and Byzantine periods before it was eventually abandoned. Evidence of ancient looting was found, but the only sign of modern use was a clay pipe installed in the 20th century.