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 three principles: 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.