A decade ago, in Sidirokastro, Serres, the cave of Mavros Vrachos was discovered, a unique geological structure that was explored for the first time by the scientific team of the Department of Geology of the Aristotle University of Thessaloniki. The exploration reached a depth of 56 meters, revealing a metallic crust with a porous structure instead of the usual stalactites and stalagmites.

This discovery was the reason for studying the cave in depth, providing valuable information about its formation and its special metallic crust. Samples from the cave were transferred to the Department of Tectonics, Historical and Applied Geology and studied in the Department of Mineralogy-Petrology-Coastal Geology of the Department of Geology of the Aristotle University of Thessaloniki. The first analyses revealed that the crust consists of the mineral goethite, i.e. iron hydroxide. The structure of goethite showed significant differences from its usual forms, which led to further investigations.

Research has revealed that the cave is a subterranean one, formed by hydrothermal fluids rising to the surface, rather than being formed by rainwater moving towards the water table in the area.

The discovery of Mavros Vrachos reveals unknown bacteria and new insights into the biological and geological history of the area

The results of this research were published in the international scientific journal CATENA and the team plans to continue their research, both in the underwater area of the cave and in the study of unknown organisms.

Part of the research was included in the doctoral thesis of George Lazaridis, supervised by Professor Vassilis Melfos of the Department of Geology. In collaboration with Dr. Dimitris Bessas from the European Synchrotron Radiation Facility (ESRF) in Grenoble, an interdisciplinary team was formed to study the cave and the particular deposit of goethite.

Also participating in the research were Professor Lambrini Papadopoulou of the Department of Geology of the Aristotle University of Thessaloniki, Professor Panagiotis Voudouris of the Department of Geology of the University of Athens, the Director of the Department of Botany of the Department of Biology of the Aristotle University of Thessaloniki, Professor Spyridon Gelis and his colleague and PhD candidate Manthos Panou.