The Idrija mercury mine in Slovenia was the second largest mercury mine in the world during its 400 years of operation (and namesake for the New Idria district in the coastal range of California). During that time, the largest documented customer for its product was the U.S. Department of Defense. Mine waste and tailings have potentially impacted soils, waterways, and marine resources of the Gulf of Trieste, Northern Adriatic some hundred kilometers downstream. Dr. Horvat will describe the numerous studies of the mine and its consequences. Dr. Milena Horvat is Head of the Department of Environmental Sciences, at the Jozef Stefan Institute, in Ljubljana, Slovenia. Dr. Horvat is an analytical chemist with extensive experience in metrology in chemistry, biogeochemistry of mercury, development of environmental monitoring and control. She previously served as head of the International Atomic Energy Agency's Marine Environmental Studies Laboratory in Monaco.