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What is the identity of the chilazon, the creature from which the techelet dye is produced? It's widely acknowledged that it is a snail by the scientific name of Hexaplex trunculus (formerly known as Murex trunculus) and known in English as the banded dye-murex. Live specimens of this snail are on exhibit in our saltwater aquarium at the Biblical Museum of Natural History:

In Tanach and the Gemara, we find various clues about the identity of the chilazon. First, we learn that it was famously produced outside of the Land of Israel, in the "Islands of Elisha" (Yechezekel 27:7), which are identified as Italy or Cyprus. Then, we have a list in the Gemara (Menachot 44a) of several aspects of the chilazon. There is debate about how well these clues match the banded dye-murex - arguments can be made in both directions. The Gemara presents the following descriptions:

  • Its body "resembles" the sea. This can be easily argued to match the banded dye-murex, which grows algae over its shell and is virtually indistinguishable from the ocean bed where it resides.

  • Its "formation" (briyato) is "similar" to that of a fish. This can be easily argued to match the banded dye-murex, whose development is only similar to a fish, in that it is an aquatic living creature that reproduces via laying eggs, but is not actually a fish.

  • The techelet dye is obtained from its "blood." This can be easily argued to match the banded dye-murex, since the Hebrew word dam can easily refer to the fluid contained in the gland of the trunculus.

  • It emerges from the sea only once every seventy years. This can easily be understood to be a figure of speech, meaning that it rarely emerges. Additionally, it may mean that it only comes close to shore rarely, and is usually in deeper waters. All this matches the banded dye-murex perfectly.

  • Due to the previous factors, it is very expensive. Dye from the banded dye-murex was indeed extremely expensive, due to the tiny amount of dye produced by each snail and the difficulty of obtaining them.

Then, elsewhere in the Talmud, we find further clues about the meaning of the word chilazon. It turns out that this is a known creature, and there are other types of chilazon which do not live in the sea (and are not a source of techelet). The Talmud says that another type of chilazon is found in the hills, and emerges in great quantities after rainfall (Sanhedrin 91a). This strongly points towards chilazon referring to a snail.

Particularly interestingly, we are told that a regular chilazon is not subject to the laws of trapping creatures on Shabbat (Talmud Yerushalmi cited by Tosafot to Shabbat 75a). Why would it have such an exception? The answer is that there is no prohibition of trapping a creature when it does not require any effort or skill. Such is the case with snails, which move so slowly that no effort is required to capture them.

At the same time, although a terrestrial snail requires no effort or skill to catch, the Talmud says that the techelet-producing chilazon was caught with a net (Shabbat 74b). This is perfectly consistent with the banded dye-murex, which were caught was by baiting nets.

Finally, we are told that techelet made from the plant-based indigo is indistinguishable from that made from the chilazon (Bava Metzia 61b). Indeed, the dye produced from the banded dye-murex is chemically identical to indigo and thus impossible to tell apart.

Now, as discussed, all these clues match the banded dye-murex. Some match it very obviously so, whereas with others, it involves arguments that to some are straight­forward but which some others dispute.

But could it be claimed that perhaps there is some other, unknown creature which matches the clues even better and is the real chilazon? Such arguments strain credulity. It is not reasonable to reject known creatures that match the clues without difficulty in favor of unknown and zoologically unlikely creatures for which, if they did exist, there would surely be some kind of evidence.

But there is an even stronger argument for the banded dye-murex. The most basic law of techelet is that it is only kosher if it is made from the correct creature; if it is made from something else, it is invalid (Tosefta, Menachot 9:6). Although – and precisely because – plant-based indigo is near-identical to techelet, the Sages stressed that one does not fulfill the mitzvah by wearing indigo (Bava Metzia 61b).

Now, it is an indisputable fact that in the Biblical and Talmudic periods, there was a famous Mediterranean trade of producing an expensive dye, chemically identical to plant indigo, and with colors ranging from purple to blue, from the banded dye-murex. There is endless archeological and historical evidence for this, and nobody disputes it.

And so the ultimate argument for techelet being derived from the banded dye-murex snail is as follows: The Sages clearly wanted to make sure that people were using real techelet and not near-indistinguishable substitutes such as plant indigo. Given that, and given that every culture was using dye from the banded dye-murex which looked the same as indigo, the Sages could not possibly have spoken about it being a marine creature and not warned against using the banded dye-murex, if the latter was not the correct creature to use.

This is why there is no doubt that Hexaplex trunculus, the banded dye-murex, is the historical source of techelet. As to whether Jewish law requires one to wear it today, that is a different matter, relating to the role of historical discovery in the reassessment of common practice. There is also room to explore whether other snails in the murex family, which live in other parts of the world, might also be an acceptable source of techelet.


On Wednesday June 26, 2024, there will be a techelet workshop at the museum - click here or on the banner below to go to the reservation page!


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