President Trump's tariffs on rare-earth metals from China should have been a boon to the only US rare-earth minerals mine in California. But a recent Wall Street Journal article illustrates that, given the complex nature of the global economy, those tariffs have actually put the Mountain Pass mine in a tough place.

A hedge fund recently bought Mountain Pass out of bankruptcy after several companies attempted to turn a profit from it. Six months later, the WSJ wrote, Trump announced tariffs that should have helped the mine supply more domestic rare-earths at a higher price.

However, most of the world's rare-earth processing facilities are in China, which also produces more than 90 percent of the world's rare-earth minerals. To develop its metals as cheaply as possible, Mountain Pass has first been shipping its ore to China, where the processed metals are then sold on the world market to makers of smartphones, laptops, and magnets that go into electric car motors and giant wind turbines.

But in September, President Trump placed a 25 percent tariff on Chinese goods entering the US, and China reacted by placing a tariff on US goods entering China. That means Mountain Pass is paying much more to have its ore made into useable products.

Now, the WSJ writes, the tariffs are eating into Mountain Pass' profit margins. "And that eats into the money Mountain Pass would be reinvesting into upgrading the facility so that it can actually process the rare earths itself, the only way to lessen dependence on the Chinese processors."

For years, China's dominance in rare-earth has been concerning for countries like Japan and the US, whose economies depend on products that depend on rare-earths. In 2014, China exercised its market power and restricted rare-earths trade, sending prices skyrocketing. Australia has recently been edging into the rare-earths market, with some significant finds suggesting that it might play a bigger role in the years to come. But until then, China holds the keys to minerals that make much of the technology we use today possible.

Industries based outside of China have been working to eliminate or reduce the need for rare-earths in their products. Toyota is an example of this, recently announcing a permanent magnet motor that uses less neodymium than previously.

Still, the US is significantly dependent on other countries for key materials. "Earlier this year, the US Geological Survey designated 35 minerals as critical to the economy and national defense," the WSJ writes. "The US is nearly reliant on imports for more than half of them."