Active geothermal systems are sources of clean energy and provide insights into ore forming processes. What are two economic geologists learning as they each pursue deep holes, big science, and audacious ideas to help provide the world’s energy needs from clean, renewable sources?  Stuart Simmons started his career in New Zealand, making key observations with big implications for low-sulfidation gold precipitation.  His recognition that platy calcite textures represent boiling zones provided a key guide to mineralization.  We talk to him about boiling, quartz pseudomorphs of calcite and what we might learn from the biggest geysers ‘never seen.’Throughout his career, Stuart has continually progressed and adapted to new systems and research.  He is currently a research professor at the University of Utah and works on the ‘Utah Forge Project’  – big science and engineering to test the possibility of deriving energy from very deep dry wells.  If it works, the audacious goal is to power Mumbai or Paris!  Along the way, the themes of heat and mass transfer keep surfacing along with the implications for understanding earth processes and ore deposit formation.  UtahFORGE In New Zealand, Isabelle Chambefort transitioned from an economic geologist who works on porphyry deposits to her current role as a Senior Geothermal Scientist, leading ‘Geothermal -The Next Generation’ Project.  Her multidisciplinary team is working to image the sub-surface in detail, to understand the circulation of deep meteoric fluids, interaction with magmas and the potential for deep wells that access currently untapped energy – where fluids are supercritical.  Another big science and engineering project with implications for the future and insights to be gained applicable to economic geology.Geothermal – the Next GenerationTheme music is Confluence by Eastwindseastwindsmusic.com