Senior Metallurgical Engineer

Location:

Boulder, CO

Reports To:

VP of Engineering and Operations

Our client is a company reinventing how the world sources critical minerals — using protein-based chemistry to extract rare earth elements and other essential materials from challenging feed stocks with unmatched selectivity. By dramatically reducing the cost and environmental impact of mineral separation, the company is making it possible to unlock new sources of supply for 21st‑century technologies. As global demand accelerates, securing these materials has become one of the most urgent challenges facing U.S. competitiveness and national security.

Backed by top investors and government partners, the team is growing fast and hiring mission‑driven scientists and engineers to help scale its platform and transform the future of mining.

We’re seeking a Senior Engineer – Metallurgical Engineering to own and advance metallurgical process development across laboratory, pilot, and commercial scales. The ideal candidate will design, optimize, and scale metallurgical unit operations including leaching, precipitation, impurity removal, roasting and calcination for rare earth elements from ores and concentrates. They will work cross‑functionally with the R&D and Engineering/Operations teams to improve yield, purity, robustness and to provide Subject Matter Expertise in the development of end‑to‑end flow sheets.

• Develop flow sheets for commercial scale plants
• Lead and support the development and commercialization of metallurgical unit operations that are quantitatively understood, scalable, and integrated with the separation platform
• Process development efforts to demonstrate improvements in recovery, purity, and process robustness driven by data and experimentation
• Work with external subject matters experts, as needed, to augment internal capabilities and to accelerate commercial timelines

• Provide Metallurgical Engineering Subject Matter Expertise to various functions of the company
• Lead the design and optimization of metallurgical flow sheets for REE‑bearing ores, concentrates, and intermediate streams
• Own unit operations including but not limited to leaching, selective precipitation, impurity removal, and calcination
• Translate bench‑scale chemistry into pilot and commercial‑scale process designs, including operating envelopes, equipment sizing, and integration with upstream and downstream systems
• Identify technical risks related to scale‑up, impurity control, reagent consumption, and solids handling, and develop mitigation strategies.
• Be equally comfortable working at lab, pilot, demo, and commercial scales, and working in silico as part of planning and analysis. Serve as a “player‑coach” who leads by example.

• Develop and maintain mass balance models across hydrometallurgical processes
• Quantitatively track yield, recovery, purity, and losses at each unit operation
• Use data to drive design decisions, trade studies, and process optimization efforts
• Support techno‑economic analysis (TEA) inputs related to hydromet processing, including reagent costs, throughput limits, and waste streams
• Develop process simulation models
• Design statistically sound experiments to improve yield and product purity
• Partner closely with Process Engineering and Analytical Chemistry teams to define sampling plans, analytical methods, and data quality requirements
• Interpret analytical data (ICP‑OES/MS, solids analysis, moisture, LOI, phase changes, particle size distribution, etc.) to inform process improvements
• Ensure experimental results are scalable, reproducible, and well‑documented

• Collaborate with Biology, Chemistry, and Engineering teams to ensure hydrometallurgy operations align with overall system performance goals
• Provide technical mentorship and review for junior engineers and scientists without formal people‑management responsibility
• Clearly communicate technical findings, risks, and recommendations to leadership and project stakeholders

• Bachelor’s or Master’s in Metallurgical…