Highlights

• MP Materials begins producing SEG+ - a high-value heavy rare earth feedstock containing strategic concentrations of dysprosium and terbium.
• The company has stockpiled over 200 metric tons of SEG+.
• Plans to activate heavy rare earth separation capabilities by next year.
• This development represents a significant milestone in re-establishing domestic rare earth processing capabilities.
• Reduces dependence on China.

In an unfolding development for America’s rare earth independence, MP Materials has announced that its Mountain Pass facility is now actively producing SEG+ — a high-value, heavy rare earth (HREE) feedstock containing strategic concentrations of dysprosium (Dy) and terbium (Tb). These two critical elements are essential for manufacturing high-temperature neodymium-iron-boron (NdFeB) permanent magnets, widely used in electric vehicle traction motors, defense systems, and advanced robotics.

SEG+ is a material produced from rare earth mines, specifically a concentrated form of HREE. It is a blend of samarium (opens in a new tab) (Sm), europium (opens in a new tab) (Eu), gadolinium (opens in a new tab) (Gd), terbium (opens in a new tab) (Tb), and dysprosium (opens in a new tab) (Dy). HREEs are a subset of rare earth elements distinguished by their unique properties and critical roles in various high-tech applications.

The significance of this milestone cannot be overstated: SEG+ represents a key enabler for the United States to re-establish domestic capabilities in the refining and separation of heavy rare earth elements, a supply chain historically dominated by China. MP Materials confirmed it has already stockpiled more than 200 metric tons of SEG+ on an oxide basis and plans to activate heavy rare earth separation capabilities as early as next year.

“This is SEG+ — the foundation of our next phase of vertical integration,” the company declared via social media, reinforcing its long-term mission to create a fully domestic rare earth-to-magnet supply chain. The feedstock, which contains roughly 4% dysprosium and terbium by total rare earth oxide (TREO), will feed into MP’s forthcoming heavy rare earth separation circuits. These facilities are being designed not only to process internal material but also to handle third-party feedstocks, positioning MP as a future central hub for heavy rare earth processing in North America.

This development follows MP’s broader expansion into magnet manufacturing and aligns with what needs to be U.S. industrial policy goals to secure critical mineral supply chains. With its high-grade SEG+ production and separation infrastructure under construction, MP is poised to close one of the most urgent gaps in American industrial resilience: the lack of domestic supply and processing of heavy rare earths required for strategic technologies.

MP Materials’ announcement that it is now producing SEG+ — a dysprosium- and terbium-rich heavy rare earth feedstock — marks a significant step toward U.S. rare earth independence. However, investors should view this milestone with strategic scrutiny. SEG+ is just the beginning. Real value depends on MP’s ability to execute complex separation processes, monetize lower-value elements such as samarium and europium, and integrate the output into its downstream Fort Worth magnet plant.

Critical questions remain. Can MP separate Dy and Tb at a commercial scale by 2026? Have pilot tests proven viable? What role will third-party feedstocks play, and are long-term offtake agreements in place? Meanwhile, regulatory hurdles, radioactive waste management (if relevant), and cost competition with China all pose challenges to raising. Of course, MP Materials' leadership understands that they must align technology, economics, and policy, as well as secure strategic buyers, for success.  Otherwise, SEG+ remains stockpiled potential, not supply chain transformation. Investors should track both throughput and tonnage.

But it’s a positive step, certainly.  For stakeholders tracking the reindustrialization of the U.S. rare earth sector, SEG+ is more than just a product — it’s a signal that the Mountain Pass renaissance is accelerating.