The Phoenician cities of Tyre and Sidon develop, around the Iron Age (10th century BC), a large-scale industry extracting purple dye from the hypobranchial glands of sea snails of the genus Murex (mainly Bolinus brandaris and Hexaplex trunculus). The process required tens of thousands of snails to produce modest amounts of dye — an estimated 12,000 specimens were needed for a single gram — making the result an extreme luxury good, worth more than its weight in silver or gold according to classical sources. The Greek name for the Phoenicians, Phoinikes, probably derives from the purplish-red color that made them famous. Vast Murex shell middens excavated on the outskirts of Sidon and Tyre confirm the industrial scale of production; the site of Tel Shiqmona, on the coast near Haifa, is one of the largest documented Iron Age production centers, though recent research from the University of Haifa suggests it may have been under the control of the Kingdom of Israel rather than directly Phoenician, evidencing regional collaboration in the industry. Tyrian purple became synonymous with royalty and authority: Roman and Byzantine emperors restricted its use by law to royalty and high magistracy.