Just how rare are rare earth elements? It depends on their price.

There are 17 REEs, with funny names like gadolinium and dysprosium—and all of them are metals.

Their special magnetic, thermal, and corrosion-resistant properties have led engineers to use them in our most familiar electronics.

The rarest ones are still 200 times more plentiful than gold. And the most common are as abundant in the Earth’s crust as nickel, zinc, or lead.

The challenge is that they’re rarely concentrated enough to mine. And when they are, it takes heavy processing with heat and acid, which produces salty, radioactive wastewater.

California was the largest producer of rare earth elements—till China entered the market.

Lower labor costs and looser environmental regulations allowed China to produce such a large supply so cheaply that U.S. mines closed.

With rare earth elements common and cheap, engineers used them in thousands of products.

But once China dominated the market, they began to raise prices and limit supply, to apply political pressure to electronics makers, like Japan.

But this backfired: Higher prices encouraged mines in other countries to reopen and discouraged engineers from using rare earth elements in new designs.

Which goes to show that rare earth elements, like all resources, are subject to the laws of economics.

Supply often depends on how much we’re willing to pay. If the price climbs beyond that, we start looking for alternatives.