Senior 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 how minerals are sourced, refined, and optimized by combining deep industrial expertise with software, automation, and data-driven decision-making. Join us as we build the future of responsible mineral sourcing and supply.

Role Overview

Mariana Minerals is looking for a highly motivated 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

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, solvent extraction, and/or similar unit operations

• Hands-on experience designing, commissioning, and starting up pilot plant or commercial scale 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

Why This Role

Mining is one of the most operationally complex industries on earth—and one of the least digitized. Most mines run on disconnected systems, tribal knowledge, and decisions made by feel rather than data.

At Mariana, you'll build the software that changes this. You'll work on autonomous haul trucks, integrated mine planning, and optimization systems that treat the entire mine as a single coordinated operation. If you want to work on hard problems with real-world stakes, this is it.

What It's Like to Work Here

Extreme Ownership – We take full responsibility for outcomes and drive relentlessly toward solutions.

Engineer Out, Then Automate – We simplify and optimize before we scale.

Share Your Legos – We collaborate openly, share knowledge freely, and help each other build better solutions.

Mariana is an Equal Opportunity Employer. We celebrate diversity and are committed to creating an inclusive environment for all employees. We do not discriminate on the basis of race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, veteran status, or any other protected status.