Powdered rocks, technically called Terrae, were extensively used in folk medicine and were at one time officially recognized in the medical profession. Some European countries, mainly Lemnos, Silesia, Italy, Germany and Malta started exporting their own terra. This they stamped with a particular seal, usually that of their ruler. The product therefore came to be known as Terra Sigillata. That from Malta was Terra Sigillata Melitensis, reputedly blessed by the Apostle Paul. It was thought to possess great magico-therapeutic powers, particularly against poison. Earth from the Grotta ta’ San Pawl in Rabat, where Paul is traditionally said to have lived and preached Christianity to the islanders, came to be attributed with enormous antipoison powers.