Does the oral tradition that identifies the hilazon as the source of tekheles necessarily indicate that one could not create the indigo-colored wool by other means? The gemara certainly indicates that the color-equivalent, plant-derived kala ilan is not valid (e.g. Menachot 40a, 43a, Bava Metzia 61b) but it also implies that this particular dye was not as fast and permanent as true tekhelet (and therefore, implicitly, was not its molecular equivalent). If that is the case, if one was able to create a dye that was chemically indistinguishable from true tekhelet, considering that torah shebiksav (the Written Law) never explicitly mentions the source of tekhelet, might that not also be acceptable?

  • Can you link to the gemara discussing kala ilan? Does it only dismiss it for that reason? – Isaac Kotlicky Apr 16 '15 at 2:15
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    Aren't you confusing the test for authenticity with a reason for it? – user6591 Apr 16 '15 at 2:31
  • I don't mean to say that that's the gemara's intent. I'm just curious to know if there is anything explicit to say that the source matters or just the substance. It's implicit from that there is a test that the substances differ. But what if we discover something that does not. (As opposed to if we invent chemically indistinguishable artificial ham, the torah clearly and explicitly forbids only the source, not the chemical compounds.) – Loewian Apr 16 '15 at 2:59
  • This is hypothetically very nogeia l'maaseh nowadays because, if artificially-dyed techeles is acceptable, and if the Tekhelet Institute is right that the dye is just murex-derived indigo, artificial indigo (used in blue jeans) is dirt cheap. – Loewian Apr 16 '15 at 3:03
  • Note that Chazal never complain about another animal source of Tekhelet, only a plant one. It seems that either they knew of no other one or that all animal sources are Kosher. – Double AA Apr 16 '15 at 3:46

This requirement is stated in the Tosefta and Meseches Tzitzith

Tosefta Menachoth 9:16

"תכלת אין כשרה אלא מן החלזון הביא שלא מן החלזון פסולה."

Tekheleth is only valid from the חלזון ; if one used a dye not made from the חלזון it is invalid.”

מסכת ציצית פרק א הלכה י

שאין צובעין תכלת אלא בחלזון.

We only dye תכלת with a חלזון

from: http://www.techeiles.org/viewer.php?filename=publications%2F%D7%94%D7%9C%D7%9E%D7%9F%2C+%D7%94%D7%A8%D7%91+%D7%9E%D7%90%D7%99%D7%A8+%D7%94%D7%9C%D7%95%D7%99+-+%D7%9C%D7%91%D7%95%D7%A9+%D7%94%D7%90%D7%A8%D7%95%D7%9F+www.techeiles.org+.pdf

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