Hexaplex trunculus degrades, resulting in blue only. Nonetheless, archeologists have confirmed Hexaplex trunculus as the species used to create the purple-blue dye; large numbers of shells were recovered from inside ancient live-storage chambers that were used for harvesting. Apparently, 10- to 12,000 murex yielded only one gram of dye. Because of this, the dye was highly prized. Also known as "Royal Purple", it was prohibitively expensive and was only used by the highest ranking aristocracy. A similar dye, "Tyrian purple", which is purple-red in color, was made from a related species of marine snail, "Murex brandaris". This dye (alternatively known as "imperial
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