Sr. Process Engineer

ABOUT MARIANA MINERALS Mariana Minerals is a software-first, vertically integrated minerals company on a mission to supply the critical minerals powering modern energy, AI, and defense technologies. We’re reimagining the minerals supply chain by combining deep industry expertise with advanced software, automation, and data-driven decision-making. ROLE OVERVIEW Mariana Minerals is looking for a highly motivated Sr. Process Engineer to join our San Francisco Pilot Plant team. You will lead the design, deployment, and operation of first-of-its-kind refining processes for critical minerals, while also supporting development of software for automated plant optimization. This position is highly hands-on and will play a critical role in bridging R&D and Operations, ensuring processes are robust, safe, cost-effective, and suitable for commercial production. WHAT YOU’LL DO - Work closely with Pilot Plant Technicians to operate, maintain, troubleshoot, and improve pilot-scale processing equipment - Design experiments to evaluate process performance, recovery, throughput, and product quality - Create and maintain key engineering and operational documentation such PFDs, HMBs, P&IDs, Operating Procedures, and Process Control Narratives - Lead equipment design scopes from concept, through procurement, fabrication, installation, commissioning, and handover to Operations - Work closely with cross-functional teams including R&D, commercial plant design engineers, project execution teams, and more to scale designs from lab to the pilot to production scale - Work closely with the software and machine learning teams to develop and implement reactor and plant optimization algorithms - Travel to pilot and commercial sites to drive commissioning, startup, and ramp-up alongside operations & plant design teams   WHAT YOU’LL BRING - B.S., M.S., or PhD in Chemical Engineering or related field - Minimum of 5 years of experience supporting R&D scale up, pilot plant operation, and/or commercial production in minerals processing, chemicals, specialty materials, oil & gas, or similar industry - Strong understanding of reaction engineering, solid-liquid separation, leaching, ion exchange, solvent extraction, and/or similar unit operations - Hands-on experience designing, commissioning, and operating pilot or commercial-scale process equipment - Ability to design experiments, problem-solve, and analyze complex datasets - Strong commitment to Health & Safety and experience with risk management, management of change, and hazard assessment - Excellent technical writing, communication, and teamwork skills - Comfort working in fast-paced, cross-functional environments OUR CULTURE IS BUILT ON FOUR PRINCIPLES: Everyone Gets Home Safe. We never put speed or cost ahead of people. Extreme Ownership. We take full responsibility for outcomes, relentlessly driving toward solutions. Engineer Out Requirements, then Automate. We simplify, optimize, and then automate for scale. Share Your Legos. We collaborate openly, share knowledge, and empower each other to build bigger, better solutions. Join us as we build the future of responsible mineral sourcing and supply!