In a rare discovery, scientists have confirmed that an almost 2,000-year-old piece of fabric found near the Dead Sea contains remnants of the Biblical blue color known as tekhelet.

It is only the third piece of fabric ever found to contain this precious blue dye derived from snail glands. In accordance with a Torah commandment, tekhelet was used in ancient times to dye the tassels, or tzitzit, attached to the four-cornered garment traditionally worn by men, as well as the clothing worn by the High Priest during the days of the temple.

The finding was revealed on Monday at a special conference held in Jerusalem to mark the 100 th anniversary of the publication of the doctorate of Rabbi Yitzchak Halevi Herzog, the former chief rabbi of Israel, on the subject of tekhelet. In attendance were many of the former chief rabbi’s grandchildren, including the keynote speaker, Isaac Herzog, the new chairman of the Labor Party.

Announcing the discovery, Dr. Na'ama Sukenik, a curator at the Israel Antiquities Authority, said the tiny piece of fabric had been discovered in the 1950s in a cave at Wadi Murba’at, where Jewish fighters hid during the Bar Kokhba revolt in the second century. As part of her doctoral dissertation at Bar Ilan University, Sukenik recently tested the color found in the fabric and was able to determine that it was derived from the Murex trunchular, a mollusk widely believed to be the marine animal known as the khilazon in the Talmud -- the source of the rare blue dye.

To this day, scientists and scholars have not reached a consensus on whether tekhelet was a light sky-blue color, as most modern day experts on the subject now believe, or a darker, more purple-hued blue. The shade discovered on the piece of fabric tested by Sukenik was sky blue. The tassels on the fragment were spun in a way that was common in Israel in ancient times, she said, demonstrating that the dye was locally produced.

“I think this is a fascinating finding,” said Baruch Sterman, a physicist and world expert on snail dying, who is also the author of “The Rarest Blue,” a recently published book on the subject. “Here we have evidence that in Israel, in the second century, they had the technology to dye blue using murex, and there was an entire industry in Israel that had all this advanced technology.”

Sterman is also the cofounder of the Ptil Tekhelet Association, an Israeli-based non-profit that produces its own line of tzitzit dyed with the biblical blue color, which its members extract from snails and process by hand.

The reason so few remnants of the dye exist from ancient times, said Sterman, is that the fragments were very fragile. “This was an industry that was lost 1,300 years ago, so if we’re going to find any remnants, they have to be at least 1,300-1,500 years old. The chances of finding them are miniscule," he added, "because the climate is so dry by the Dead Sea and because of the chemicals in the air there, you can find things older there than in other places."

There is no evidence, he said, that other two pieces of fabric containing the blue dye derived from the murex were produced in ancient Israel. One fragment, containing a light blue color, was discovered in the Pazyrik region of Russia, and the other, containing a darker blue, was discovered during the Masada excavations. The fragment discovered in Masada, he said, may not necessarily have been produced locally.

Open gallery view Tzitziot traditionally have light blue tassles.