70 years, and with its blood tekhelet is dyed, therefore it is expensive." Dye was extracted from the Ḥillazon by cracking it open, suggesting that it has a hard external shell. Just as the Hebrews' clothing did not wear out in the desert (), the shell of the Ḥillazon does not wear out. Garments tied with tekhelet and indigo have such similar appearance that only God can distinguish them. Elsewhere, one opinion says that there is no chemical test which can distinguish between tekhelet and indigo wool, but another opinion describes such a test and tells the story of it working successfully. Trapping the Ḥillazon is considered a violation of Shabbat. In the time of the Talmud the hilazon was used as part of a remedy for hemorrhoids, though this may refer to a different species of snail. Various animals have been suggested as the ḥillazon. Bonellia Viridis See the following link for more info.Chilazon Hexaplex trunculus In his doctoral thesis (London, 1913) on the subject, Rabbi Yitzhak HaLevi Herzog named Hexaplex trunculus (then known by the name "Murex trunculus") as the most likely candidate for the dye's source. Herzog concluded “it is very unlikely that the tekhelet-hillazon is not the snail called murex trunculus, but though unlikely, it is still possible.” Though Hexaplex trunculus fulfilled many of the Talmudic criteria, Herzog's inability to consistently obtain blue dye (sometimes the dye was purple) from the snail precluded him from declaring it to be the dye source. In the 1980s, Otto Elsner, a chemist from the Shenkar College of Fibers in Israel, discovered that if a solution of the dye was exposed to ultraviolet rays, such as from sunlight, blue instead of purple was consistently produced. In 1988, Rabbi Eliyahu Tavger dyed Tekhelet from H. trunculus for the Mitzvah (commandment) of Tzitzit for the first time in recent history. Based on this work, four years later, the Ptil Tekhelet Organization was founded to educate about the dye production process, and to make the dye available for all who desire to use it. The television show The Naked Archaeologist interviews an Israeli scientist who also makes the claim that this mollusk is the correct animal. A demonstration of the production of the blue dye using sunlight to produce the blue color is shown. The dye is extracted from the hypobranchial gland of Hexaplex trunculus snails. Chemically, exposure to sunlight turns the red