(ANSA) - Capri, August 17 - A sunken vessel bearing a load of obsidian dating back thousands of years has been discovered in the sea off the southern Italian island of Capri. The ship is probably one of the oldest maritime relics found in the Mediterranean basin to date, according to the diver who found the ship. "The cargo has been under water now for more than 5,000 years," Vasco Fronzoni claimed. "The discovery could force the revision of historical knowledge relating to the routes of commerce in antiquity," he added. Fronzoni immediately alerted the Italian culture authorities about his find. Capri is located in front of the Gulf of Naples. Obsidian is a purple-black rock formed as a result of cooled magma. It used to be used in ancient times to build arms and utensils prior to the discovery of metals. Of all the islands on that section of sea, Capri is the only one not of volcanic origin. Fronzoni is a Capri native.