Here’s an idea you see spreading across the internet every so often: that all semiconductor and solar PV manufacturing depends on extremely pure quartz from the town of Spruce Pine, North Carolina. This quartz is used to make the crucibles which hold the molten silicon as it gets turned into silicon ingots, which are then cut into wafers and made into chips. The quartz needs to be very pure to prevent impurities from seeping into the silicon, and Spruce Pine is where this very pure quartz comes from.
Spruce Pine quartz started to get major attention after it was mentioned in Ed Conway’s 2023 book Material World, though it was also mentioned in Vince Beiser’s 2018 book The World in a Grain. Interest spiked following Hurricane Helene amidst concerns that flood damage to the Spruce Pine mines might shut down supply: articles showed up in places like NPR, Forbes, and Axios.
Flooding in downtown Spruce Pine after Helene, via The Mitchell News .
Spruce Pine quartz is often discussed in apocalyptic terms. The implication is that if something happened to the mine, semiconductor manufacturing (and possibly the world economy) would grind to a halt while we scrambled to find a substitute. In his tweet above, Mollick says that “The modern economy rests on a single road in Spruce Pine, North Carolina.” In Material World, Conway quotes an industry expert who says that sufficient damage to the mines “could end the world’s production of semiconductors and solar panels within six months.”
Location of Spruce Pine, via Google Maps.
Is this true? Sort of. Quartz crucibles are indeed necessary for most semiconductor manufacturing, and Spruce Pine is where most of this quartz comes from. Spruce Pine quartz isn’t quite an irreplaceable linchpin in semiconductor manufacturing. But alternatives are all some combination of not yet developed, not quite as good, and not quite as cheap. Cutting off the supply of Spruce Pine quartz probably wouldn’t choke off the supply of semiconductors completely, but it would mean yields going down and costs going up. The industry is aware of the bottleneck: new sources of quartz are being developed, and new crucible materials are being investigated. A new crucible material, if found, would have a particularly large impact: not just because it would eliminate the Spruce Pine bottleneck, but because quartz is a major limiting factor in silicon ingot manufacturing, and a new, better material could potentially increase production efficiencies dramatically.
Semiconductors and high-purity quartz
Production of metallurgical silicon, via link .
Most modern semiconductors are made from very high-purity silicon: 99.9999999% (known as 9N) pure for microchips, and somewhat less pure (6N-8N) for solar cells. Getting silicon to this level of purity requires multiple refining steps. The process starts with quartz (silicon dioxide), which is reacted with carbon in a submerged arc furnace to produce metallurgical grade silicon (around 98–99% pure). Metallurgical silicon is then run through the Siemens process: silicon is reacted with hydrogen chloride to produce gaseous trichlorosilane (SiHCl3), which then gets liquified, evaporated back to gas, and exposed to heated silicon filaments in the presence of hydrogen gas. The silicon condenses on the filaments via chemical vapor deposition, creating rods of very pure polysilicon, silicon made up of multiple crystals with intersecting boundaries.
Siemens process for polysilicon production, via link .
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