Graphite nanoplatelets (GNPs) react with elemental sulfur to provide a mechanically stable, spongy material characterized by good electrical conductivity and high surface development; such unique property combination makes these novel nanostructured materials very useful for applications in different technological fields. The carbon-sulfur reaction can be accurately investigated by thermal analysis (differential scanning calorimetry and thermogravimetric analysis) and energy-dispersive X-ray spectroscopy combined with scanning electron microscopy. The thermal treatment required for the formation of electrically conductive monosulfur connections among the GNP unities has been investigated. PACS: 81.05.Ue, 81.05.Rm, 81.16.Be.