The walls of the mine are damp and moldy. They are apparently rich in the nutrients needed by the penicillin mold. It thrives inside the mine. According to Dona Bárbara, the slaves who worked the mine were free of lung infections due to the presence of the penicillin. You can see it growing in white splotches. It is present in great quantities in the illuminated parts of the mine. I didn´t see any growing in the abandoned, dangerous, pitch-black areas of the mine. Before electricity, the mine was illuminated by fish and whale oil lamps.