The treasure needed to be secured. So the hoard of 425 gold coins was stowed in a clay jar, its lid secured with a nail, and stashed in the sands of what is now central Israel.

It then sat undisturbed for more than 1,100 years, until last week, when two 18-year-olds taking part in an archaeological excavation by a hillside in Yavneh noticed something unusual.

“I dug in the ground and, when I excavated the soil, saw what looked like very thin leaves,” said Oz Cohen, one of the teenagers. “When I looked again, I saw these were gold coins. It was really exciting to find such a special and ancient treasure.”

The teenagers were volunteers in a vast project linked to the construction of a community in Yavneh, south of Tel Aviv. The program offers the promise of connecting young people with history, and, while it is meant to be culturally rewarding, it is not often that someone strikes gold — literally.

In fact, Robert Kool, a coin expert at the Israel Antiquities Authority, said the find was a “rare treasure” that could help archaeologists gain a deeper understanding of what was happening in the region at the time.

The coins, which weigh less than two pounds and are made of pure gold, date to the ninth century, when the Abbasid Caliphate ruled a vast empire stretching from Persia in the east to North Africa in the west.