About that Spruce Pine (NC) Quartz Mine Story

One of the stories that immediately caught my attention as soon as the reports from the Hurricane Helene disaster started coming in was the one about how a small quartz provider in Spruce Pine being shut down had the potential to shut down all semiconductor manufacturing and seriously impact the modern world.  

Let me repost the first story I ever saw on this, from Virtual Mirage on October 1st one of my daily (or more) reads:

In March, a Wharton professor who studies artificial intelligence and start-ups claimed on X, “The modern economy rests on a single road in Spruce Pine, North Carolina. The road runs to the two mines that are the sole supplier of the quartz required to make the crucibles needed to refine silicon wafers.” Ethan Mollick noted at the time, “There are no alternative sources known” if supply disruptions were seen in Spruce Pines. It looks like rail and road in the area are gone, along with a chunk of Spruce Pines. [NOTE: that statement that there are no alternative sources known is contradicted by another reference I've found that says there are two large sources in India and Brazil. - SiG]

This was forwarded to Larry at VM by a friend and he noted some immediate questions about it in the comments, in particular that quartz is a "simple compound, SiO₂ with a (relatively) low melting point so that it can be made in an autoclave or similar industrial oven. Silica is the second most common mineral on the planet, so there is no shortage. I think that the industrial application finds it less expensive to mine." All of that is exactly correct. Further, every part of "modern electronics" you have, be it computer, tablet, iPad, Kindle, your phone, everything, already relies on a quartz crystal.  

As a radio designer, I couldn't tell you the number of quartz crystals, as just components I've built into oscillators (sources of radio frequency on specific frequencies) or purchased as already-built components. This goes back to the early 1980s. While in the never-ending search for ways to take costs out of computers and other consumer items, there has been a move toward less accurate ways to create a master clock for everything in the computer (or whatever), crystals still have their place where frequency accuracy is important.  It's not unusual to buy a crystal specified as some frequency even in the "several hundred" MHz range and specified to within a small number of Hertz. An off the shelf clock oscillator may be specified to within 25 parts per million (25 ppm), a temperature compensated crystal oscillator (TCXO) may be specified to 1/2 ppm or less. (For example, a 10.000000 MHz crystal to 1/2 ppm will be within + 5 Hz of that at all times.) The most tightly controlled oscillators are Oven Controlled Crystal Oscillators (OCXO) and they are more stringently specified. (TCXOs run at the ambient temperature but have their frequency drift controlled with some clever circuit design; OCXOs run at a high (higher than the ambient temp rating) temperature and reduce variation by locking the temperature, and using quartz cuts optimized for that temperature - as well as some clever circuit design).  

I can't give a precise date but I don't believe a quartz crystal resonator or oscillator has been made with slices of quartz crystals out of the ground since the 1970s.

The article that many have referred to appears be this one on Wired by Vince Beiser. There's a vast misunderstanding or failure to communicate. This is what the source article is referring to as coming from Spruce Pine's deposit of high purity quartz (HPQ):

Rocks like these high-grade silica samples mined near Charlotte, North Carolina, are the basis for the quartz crucibles being discussed.  Image credit: Charles O'Rear/Getty Images

This lab-grown quartz crystal is what the crystals used in oscillators, crystal filters and other circuits are cut from. Millions of these have been made to cut crystal blanks from. This is a sample of an early effort to grow crystals at Bell Labs in 1956. Image credit Weinrich Minerals.  The rusted steel on both ends (more visible on the right) held a "seed" crystal for the new crystals to grow on.

Yes, the wired article referred to quartz crucibles used for purifying Silicon, not creating oscillators and other resonators. The crucibles look more like the rocks in the first picture - not a crystal structure like that. I interpret that to mean the crucibles are made from polycrystalline quartz and not a single big crystal like the one above. 

Notice the white rim (most prominent at the bottom front and top back) surrounding the silvery chunks of silicon? That's the crucible.  

The point is that the crystals grown for those other uses have been purified. Everything that reduced the purity of the crystals they started with has been removed.  If it can be done for that use, it can be done for crucibles or any other use. 

What's going on here is strictly economic. The silicon wafer makers would rather take the high purity quartz (HPQ) or ultra-pure quartz mined in Spruce Pine (or a few other places in the world) to make the crucibles from than purify lower grade quartz. How big those cost trades are, including going to "slightly lower quality quartz" or importing from the other couple of places on earth, is never talked about.