Tyrian purple the Iles Purpuraires at Mogador, in Morocco. The sea snail harvested at this western Moroccan dye production facility was "Hexaplex trunculus" (mentioned above) also known by the older name "Murex trunculus". This second species of dye murex is found today on the Mediterranean and Atlantic coasts of Europe and Africa (Spain and Portugal, Morocco, and the Canary Islands). The colour-fast (non-fading) dye was an item of luxury trade, prized by Romans, who used it to colour ceremonial robes. Used as a dye, the color shifts from blue (peak absorption at 590 nm, which is yellow-orange) to reddish-purple (peak absorption at
HMS Tyrian (R67) and ratings. The ship was armed with four 45-calibre 4.7-inch (120 mm) Mark XII guns in dual-purpose mounts. For anti-aircraft (AA) defence, "Tyrian" had one twin mount for Bofors 40 mm guns and four twin Oerlikon autocannon. She was fitted with two above-water quadruple mounts for torpedoes. Two depth charge rails and four throwers were fitted for which 70 depth charges were provided. Between 1946 and 1951 "Tyrian" was held in reserve at Harwich. Between 1951 and 1952 she was converted to a Type 16 fast anti-submarine frigate, by Harland & Wolff at Liverpool. She was also allocated the new