TEKHELET (Heb. תְּכֵלֶת; "blue"), argaman ("purple"), and tola'at shani ("*crimson worm") are frequently mentioned together in the Bible as dyestuffs for threads and fabrics, including the curtains of the Tabernacle (Ex. 26: 1), the veil (Ex. 26:31), the veil for the tent (Ex. 26: 31) and the ephod (Ex. 28:6). A thread of tekhelet had to be included in the fringes (Num. 15: 38). Princes and nobles wore garments of tekhelet (Ezek. 23:6) and it was used for the expensive fabrics in the royal palace (Esth. 1:6). The Tyrians were expert dyers with these materials (ii Chron. 2:6; cf. Ezek. 27:7). According to the talmudic aggadah, the dwellers in Luz (a legendary locality) were experts in dyeing tekhelet (Sanh. 12a; Sot. 46b). Tekhelet was extracted from the ḥillazon – a snail found in the sea between the promontory of Tyre and Haifa (Shab. 26a; Sif. Deut. 354). Members of the tribe of Zebulun engaged in gathering it (Meg. 6a), and according to the Midrash, it is this which is referred to in that tribe's blessing that their inheritance would include "the hidden treasures of the sands" (Deut. 33: 19). The baraita notes that the tekhelet multiplies like fish, i.e., by laying eggs, "and comes up once in 70 years, and with its blood tekhelet is dyed, and that is why it is expensive" (Men. 44a; cf. Sif., ibid.). The statement reflects the fact that the snail reaches the shore in shoals infrequently and the extraction of the dye is a very expensive process. For this reason "a garment made wholly of tekhelet" was considered expensive and rare (Men. 39a, etc.).
The color of tekhelet was between green and blue and was thus described: "Tekhelet resembles the sea, the sea resembles grass, and grass resembles the heavens" (tj, Ber. 1:5, 3a). It is like the color of the *leek. Tekhelet was usually dyed on wool (Yev. 4b). The color was fast and withstood oxidization (Men. 42b–43a). The best dye was obtained when extracted from live snails (Shab. 75a) and to make it fast various materials were added (Men. 42b). In the time of the Mishnah another dye, kela ilan, extracted from the Indian indigo plant, was introduced into Ereẓ Israel. This dye is very similar in color to tekhelet but is much cheaper. Thenceforth indigo was frequently used to counterfeit, and was sold as, tekhelet. Ways of testing to distinguish them were indeed suggested, but the baraita concluded that "There is no way of testing the tekhelet of ẓiẓit, and it should be bought from an expert" (Men. 42b). It is worthy of note that dyed ẓiẓit were discovered in the Bar Kokhba Caves. The testing of them by modern methods proved almost with certainty that they were in fact dyed with indigo – the aforementioned kela ilan. For all these reasons – the high cost of tekhelet, the difficulty of gathering the snails and extracting the dye, and because of the fear of counterfeiting with kela ilan – some tannaim permitted ẓiẓit made without a thread of tekhelet (Men. 4:1; cf. Men. 38a). It is probable, however, that many continued to fulfill the biblical precept. In the time of the amora Abbaye, Jews still engaged in dyeing with the tekhelet and Samuel b. Judah, a Babylonian amora who had resided in Ereẓ Israel, explained the dyeing process to him. In the time of the savora Aḥai the differences between tekhelet and kela ilan were tested (Men. 42b). The Midrash, however, notes that "nowadays we only possess white ẓiẓit, the tekhelet having been concealed" (Num. R. 17:5).
Gershon Ḥanokh Leiner, the ḥasidic rabbi of Radzin, proposed in his books Sefunei Temunei Ḥol (1887) and Petil Tekhelet (1888) that the precept of the tekhelet in ẓiẓit be reintroduced. He came to the conclusion that tekhelet had been extracted from the cuttlefish, Sepia officinalis (vulgaris), which has a gland in its body that secretes a blue-black dye, and his suggestion was adopted by his followers. From the sources, however, it seems that the tekhelet dye was much lighter, and the descriptions of tekhelet in rabbinical literature do not fit this creature, which is common on the shores of Israel, its dye being neither expensive nor fast. It is also difficult to identify it with the ḥillazon. Ḥillazon in rabbinical literature is a land or sea snail (Sanh. 91a). Among the latter there are species in whose bodies is a gland containing a clear liquid, which when it comes into contact with the air becomes greenish: this is tekhelet which, after the addition of various chemicals, receives its purple color, the "royal purple" of literature. The Phoenicians in particular specialized in it, Phoenicia in Greek meaning the land of purple. Around Tyre and Ras-Shamra – the site of ancient Ugarit – large quantities of shells of the purple snail have been found. These belong to the species Murex trunculus and Murex brandaris, which are found along the length of the eastern shore of the Mediterranean and whose quantities change from time to time. A modern investigator extracted 1.4 gram of the purple dye from 12,000 such snails, thus explaining the high cost of the tekhelet and purple dyes. Isaac *Herzog, in a study of tekhelet ("The Dyeing of Purple in Ancient Israel," 1919; see bibliography), reached the conclusion that it was extracted from the snails Janthina pallida and Janthina bicolor that are found a considerable distance from the shore and only reach it at long intervals. This in his opinion explains the statement that the tekhelet comes up once in 70 years (Men. 44a). The dye extracted from these snails varies between violet blue and the blue of the heavens. Most investigators incline to the view that tekhelet and argaman were extracted from the Murex snails.
Krauss, Tal Arch, 1 (1910), 146–7; S. Bodenheimer, Ha-Ḥai be-Arẓot ha-Mikra, 2 (1956), 305ff.; M.M. Kasher, in: Sefer ha-Yovel … Eliyahu Jung (1962), 241–58; J. Feliks, in: Talmud El-Am – Berakhot (1965), 173–4; I. Frenkel, Men of Distinction, 1 (1967), 51–57. add. bibliography: Feliks, Ha-Ẓome'aḥ, 230, 284, 285; I. Herzog, The Royal Purple and the Biblical Blue: The Study of Chief Rabbi Isaac Herzog and Recent Scientific Contributions, ed. E. Spanier (1987).