His fame as a preacher caught the attention of Vincent Ferrer who once visited him and the two discussed spiritual matters at great lengths. Geremia was seen as one of the finest preachers on the island and preached in the open often because the churches never could hold the vast number of people that flocked to see him. On one particular occasion there was no food for the people and he asked a fisherman for a donation but the fisherman refused him in a rude manner. So he got into a boat and rowed out to sea and made a sign to the fish who broke the nets in the water and followed him back to the shore. The fisherman apologized and so he made another sign to the fish who returned to the nets in the sea. On another occasion he was preaching on repentance in Catania when Mount Etna erupted in 1444; the people begged him to save him and he went to the Saint Agatha shrine and removed the saint's veil. He held the veil towards the flow of lava heading towards the town and the eruption and lava flow ceased.