Ni-Co 2025 is the second of three volumes devoted to the Copper 2025 + Ni-Co 2025 + Cross-Cutting Symposia of the Extraction 2025 Meeting & Exhibition joint conference, held November 16-20, 2025, at the Sheraton Grand at Wild Horse Pass in Phoenix, Arizona, USA. The Extraction 2025 volumes collect important research examining new developments in foundational extractive metallurgy topics and techniques. They also offer new programming designed to share the latest research and insights on emerging technologies and issues that are shaping the global extractive metallurgy industry. The Extraction 2025 Meeting & Exhibition was jointly organized by The Metallurgy and Materials Society (MetSoc) of the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), the Society for Mining, Metallurgy & Exploration (SME), and The Minerals, Metals & Materials Society (TMS).