Quartz is the second-most abundant mineral in the Earth’s crust, but while it can be found across the world, quartz reserve properties—including a deposit’s size and type—vary by region. It is rare to find economically viable deposits of HPQ. Aside from Spruce Pine, the largest are found in India and Brazil.

Another silicon material, so-called silicon metal—a lower-grade and more easily accessible material that is largely sourced in China—is also listed as a critical raw material for the silicon industry by the European Commission, the UK, India, and South Korea. But it is unclear what percentage of it is refined for use in computing. “HPQ from Spruce Pine is, in a way, more critical and valuable because of its purity,” says Jonnie Penn, an associate professor of AI ethics and society at the University of Cambridge.

“Its unique purity emerges out of processes that unfold over geological rather than human timescales,” Penn says. “This purity requirement matters most for advanced computing systems in areas like the military, health care, and quantum computing.”

The two main companies at the Spruce Pine pegmatite complex—roughly 40 kilometers long by 16 kilometers wide, according to a 1962 survey—are Quartz Corp and Unimim, a subsidiary of the global industrial minerals company SCR-Sibelco, based in Belgium.

A spokesperson for Sibelco said, “As of September 26, we have temporarily halted operations at the Spruce Pine facilities in response to these challenges.

“We are working closely with our local team to safely restart operations as soon as we can and are actively coordinating with local authorities and other partners to manage the situation. Our top priority remains the health, safety, and well-being of our employees, as well as ensuring the security of the Spruce Pine facility.”