Other means of obtain the colour dye from a type of cuttlefish call Hillazon “The hillazon is this: its body is like the sea, its creation is like fish, it comes up once in seventy years and with its blood one dyes tekhelet - consequently it is expensive”.(Menacchott 44a) read more from this article http://www.tekhelet.com/pdf/braita.pdf The fishers of the hillazon are from Haifa to Tzur (Tyre). (Shabbat 26a). How are dye made? http://www.tekhelet.com/criteria.htm
In the Talmud, (Tractate Menchot 44a, the chilazon is described as follows:  :
Other criteria (with Talmudic references):
The Mystery of Tekhelet is a fascinating documentary that takes the viewer on a journey through history in search of the ancient blue dye, Tekhelet. The movie, richly filmed, travels through 3000 years of Jewish history. Come see scuba divers collecting the snails of Tekhelet off the coast of Israel. Observe Bedouin shepherds shearing sheep. Participate in sophisticated chemical analysis of the dyes as well as the actual dyeing of Tekhelet in a 2500 year old Tekhelet factory.
The Biblical commandment of Tzitzit and Tekhelet becomes meaningful in a profound way in P'til Tekhelet's The Mystery of Tekhelet.