Discovery of Mysterious Cave Pearls in Jerusalem Reveals Ancient Artifacts Trapped in Stone

A team of archaeologists has made an unexpected and groundbreaking discovery deep within an ancient underground tunnel in Jerusalem. While exploring the tunnel’s depths, researchers stumbled upon a phenomenon never before documented—cave pearls naturally formed over centuries, encasing archaeological artifacts within their mineral layers. Among these preserved relics are pottery shards and ancient plaster fragments, offering a rare glimpse into civilizations that once thrived in the region. This remarkable find not only challenges previous understandings of cave formations but also sheds new light on the long-hidden history of one of the world’s oldest and most significant cities.

Study reveals groundbreaking discovery

The discovery was made during an archaeological study led by Dr. Azriel Yechezkel of the Hebrew University of Jerusalem, in collaboration with researchers from Tel Aviv University. Their findings were published in the journal Archaeometry in December 2024.

The research took place in the Joweizeh spring tunnel (ST), an ancient man-made tunnel designed to extract groundwater near Jerusalem’s Old City. This tunnel, spanning 232 meters, is considered one of the longest and oldest in the southern Levant. While the team was initially focused on surveying the tunnel for artifacts, they stumbled upon something far more unique—cave pearls embedded with human-made objects.

“Our initial research focused on mapping and surveying for archaeological artifacts within the spring tunnel,” said Dr. Yechezkel. “Cave pearls, a rare type of speleothem, were not the primary objective of our investigation. 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.”

What Are Cave Pearls, And Why Is This Find unique?

Cave pearls are a rare type of speleothem, or cave mineral deposit, which form when water drips onto a nucleus—such as a grain of sand—causing mineral layers to build up over time. Unlike stalactites and stalagmites, which take thousands of years to form, cave pearls can develop in just a few hundred years under the right conditions.

In the Joweizeh spring tunnel, researchers uncovered 50 cave pearls, 14 of which contained pottery shards, while two contained ancient plaster. This marks the first known case of cave pearls forming around human-made artifacts, effectively sealing them within layers of mineral deposits.

Pottery fragments spanning multiple civilizations

Further analysis revealed that the embedded pottery fragments date back to different historical periods, including the Hellenistic (333–63 BCE), Roman (63 BCE–324 CE), and Byzantine (330–636 CE) eras. Additionally, some fragments may trace as far back as the Middle Bronze Age II (ca. 17th century BCE) or even the Babylonian and Persian periods.

“Despite our efforts, we could not definitively identify the remaining pottery fragments embedded in the cave pearls,” said Dr. Yechezkel. “Nevertheless, it is evident that these fragments span various historical periods and are composed of a range of materials.”

Among the most intriguing discoveries were two pottery fragments coated in cobalt, a rare and expensive material not commonly used in local ceramic production. Such pottery has been previously linked to Cyprus and Ephesus (modern-day Turkey) in the second and first centuries BCE, where it was used for luxury ceramic lamps.

How Did An Expensive Lamp End Up in An Underground Tunnel?

The presence of an imported cobalt-coated lamp fragment raises questions about how such an object ended up in a water tunnel used primarily for engineering and labor. Dr. Yechezkel suggests that it may have belonged to an engineer overseeing the tunnel’s construction and maintenance.

“It’s my hypothesis that the manual labor of excavating and removing the debris was carried out by the workers. Yet, the overall project was undoubtedly overseen by engineers with expertise in hydrology and geology,” he explained. “Evidence of such engineers, though from later time periods, has been discovered in numerous other tunnels both in Israel and internationally. The imported lamp could have belonged to one of these engineers.”

This insight provides a glimpse into how ancient infrastructure projects were managed, suggesting that skilled professionals played a crucial role in their execution.

The Long History of the Joweizeh Spring Tunnel

Analysis of the tunnel’s architecture and artifacts indicates that it was first constructed during the Iron Age II (8th–7th centuries BCE), likely as part of a royal estate near Jerusalem. The tunnel continued to be used and maintained through the Babylonian conquest (586 BCE), the Persian period (586–333 BCE), and the Hellenistic era.

During the Hellenistic period, it appears the tunnel underwent significant renovations, as indicated by the plaster and pottery fragments embedded in the cave pearls. It remained in use through the Roman and Byzantine periods before eventually being abandoned.

Though looting may have occurred over the centuries, there is no significant evidence of modern use aside from a 20th-century clay pipe installation running through the tunnel.