Mining giant Brazil has big ambitions to build a rare earths industry as Western economies push to secure the metals needed for magnets used in green energy and defense and break China's dominance of the supply chain.

Working to its advantage are low labor costs, clean energy, established regulations and proximity to end markets, including Latin America's first magnet plant which would provide a ready buyer for the metals.

But low rare earths prices, technical challenges and nervous lenders pose challenges to the Latin American nation's hopes to propel itself into the world's top five rare earths producers.