In a squat warehouse not far from the Atlantic shoreline in La Rochelle, France, sits a cluster of giant metal tanks topped by gently whirring motors.

They are a gamble on the future of European industry.

Since April, the tanks have been purifying two rare earth minerals: a hot pink solution called neodymium and lime-green praseodymium. Both are turned into powder and then sold for use in permanent magnets — crucial materials in producing modern cars, wind turbines and military equipment.

For now, the quantities being produced are experimental and tiny. Solvay, the Belgium-based company that owns the plant, will increase production only if it can find customers. “We are just here signaling that we are available to Europe,” said Philippe Kehren, Solvay’s chief executive officer.

The company is an example of an unfolding trend. Europe is trying to get back into the rare earths business, but the barriers are towering, and whether it will succeed is uncertain.

Rare earth minerals are critical components to advanced technologies in industries including energy and transportation. Magnets made with rare earths are particularly powerful and resistant to heat, making them useful in small electric motors and other applications. Most of these 17 important elements — difficult and often dirty to mine and refine at scale — come from China, which has spent decades becoming the dominant producer.