Tekhelet and the Banded Dye-Murex in Halakha

The Sages determined two criteria in regard to the tekhelet:

  • a

    "Tekhelet is kosher only when produced from a snail: that which is produced from any other source is disqualified” (Tosefta Menachot, 9, 6).

  • b

    “And now we do not have tekhelet, but only white, because the source of the tekhelet has disappeared” ” (Midrash Bemidbar Raba, 17, 5 and Tanchuma Shlach 15).

These two fundamental rulings are uniquely authentic tekhelet traditions and, accordingly, should be the deciding criteria in research to determine the identity of tekhelet.

The validity of the “disappearance of tekhelet” test (criterion 2, above) is clearly expressed in the critique of the Rabbi of Radzin's attempt to identify the hilazon snail, as presented by Beit HaLevi, Rabbi Dov Yosef of Brisk, and as quoted in “Ein HaTekhelet”, written by the Rabbi of Radzin himself:

"He did not clarify in his writings what it was that he discovered after it had been forgotten, if it was discovery of the fish or production of the dye For only after clarifying this, that is to say if there was something forgotten that he had discovered, only then will we be obligated to listen to him and wear it.
"Indeed, if we say that this fish existed and also the production of its dye was known throughout the times that have passed since tekhelet was lost to the Jewish People, and even so our forefathers did not wear tekhelet, this is as if we have a tradition and Messora from our forefathers that this fish and its dye are not the snail and the tekhelet, even though it has all the characteristics stated for it by our Sages. Thus, even if we have evidence as plentiful as the sand on the sea, we cannot argue against tradition and Messora.
"Only after he clarifies to us that this fish was forgotten or the production of its dye ceased at any time in the past and thereby the tradition stopped, then we can use halakha as evidence.”

It is thus determined unequivocally that the above-mentioned historical criterion (disappearance of the tekhelet) is decisive and definitive; while, on the other hand, one must reject the identification of the snail and tekhelet that is based only on the characteristics quoted in the Talmudic sources Menachot 44a: “The hillazon resembles the sea in its colour, and in shape it resembles a fish; it appears once in seventy years, and with its blood one dyes the tekhelet; and therefore it is so expensive.”

It is especially exciting to note that such a reliance on the “characteristics” test has also been rejected by Rabbi Levy Yitzhak Halperin, Head of the Scientific Technological and Halachic Institute in Jerusalem. In his responsum on the renewal of the tekhelet in tzitzit, he discusses the identification of the tekhelet by expounding the Talmudic principle: “Identification by visual impression is more reliable than identification by a distinguishing mark” (Tractate Chulin, 95b):

”We must judge more by visual evidence than by characteristic signs, according to the Talmud (Tractate Chulin 95b) regarding the difference between between visual impression and distinguishing characteristics.
"Thus we have tangible evidence of the great enterprise of dyeing with snails in the Tyre area, as it is mentioned in the sources regarding the tekhelet snail, as stated by Rabbi Isaac Halevi Herzog: “this is where it was found, this is where it existed”, that this is clear proof, and using visual impression to a reliable extent. In light of this we must discuss the basic and practical proof, which is over and above these signs, and that it is the snail that thousands of its shells are found in that location, and this is more significant than the signs. And if we could manage to explain with the Sages’ signs and their descriptions of the tekhelet snail, we could determine that this is the snail about which they spoke.
"In particular, we must explain the Sages’ test and the Rambam’s quote regarding the laws of tzitzit that the colour keeps its beauty even after several washes. Dr. Ziderman referred to this matter in his publications on the signs mentioned by the Sages and also in other articles he wrote about the signs, the beauty and the other marks after quoting the Rambam “and the abovementioned tekhelet must be dyed in a manner that maintains its beauty and does not change“ (Laws of Tzitzit, Chapter 2, 1) The purple dye in the body of the Janthina is not suitable because the chemical composition does not provide a fast dye. The blue dye from the cuttlefish is not resistant to washing. On the other hand, the blue and purple derived from the banded dye-murex, belonging to the chemical compound indigo, were the most beautiful and stable colours in the ancient world.
”He also writes that the way to explain the signs of the Sages and the words of Rambam was that they matched the banded dye-murex."

Rabbi Halperin therefore determines that the scientific and historical findings are preferable to the “characteristic feature signs” test.
Rabbi Tzvi Hershel Shechter also provides halakhic support from the Gemara, for relying on science and archaeology in determining the source of the tekhelet (Nefesh HaRav, Note 26).

As a result of the break in continuity of tekhelet-use, the identity of the tekhelet was lost ever since. It follows that those who wrote about the issue of the tekhelet after the times that the identity of the tekhelet was lost, did so without having seen the snail, or the tekhelet, or the process of dyeing the tekhelet, or the method of tying the tassels of the tzitzit. Therefore, later sources on this subject are not direct testimonies, but rather later interpretations of the original Talmudic sources. In a historical study one must, therefore, refer to the later sources accordingly and rule according to the two above-mentioned criteria that were written by our Sages.
Identification of the ancient tekhelet will be discovered from a study that aims to find historical proof of the existence of a Mediterranean marine snail on a scale enabling mass production of dyed fabric, over a period of 3,000 years, until the loss of the tekhelet 1,300 years ago. This study has brought about the clear-cut and unequivocal result that the biblical snail is, in fact, the banded dye-murex, also known as Murex trunculus.

Following this identification of the snail, we can now suitably deal with the braita in Tractate Menachot (44a) and the rulings of the Rambam (Laws of Tzitzit, Chapter 1, Halacha 2) – in order to understand the four characteristics of the snail as there. Our findings were published in Ha’Maayan, 5755:

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We recently discovered that the main component in the tekhelet is a natural chemical known as 6-monobromo-indigotin (MBI), which is unique in the fact that gentle heating spontaneously changes its hue from violet to blue, giving us the required shade, similar to the oriental hyacinth flower.