[missedthecue]

The US imports massive amounts of silicon (from countries like Russia no less). We do not have our own supply.

And no, rare earths are not contained in semiconductors specifically, but I assumed the parent comment wants to onshore more production than solely semiconductors, and rare earths are needed for lots of essential electronics.

[kragen]

Yes, the US has its own supply of silicon. Toledo, Ohio, was called the "glass center of the world" in the 01930s because of the combination of cheap energy (natural gas), low freight rates, and the high-quality silicon-dioxide sand mined at Silica, Ohio, twelve miles to the west (10.2307/141587). The US is the world's leading producer of silica, producing about 100 million tonnes per year and exporting 4 million (https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-sand-grave...), ten times the 0.4 million tonnes it imports. The world's highest purity silicon dioxide deposits are at the Spruce Pine mine in North Carolina, and these are commonly used to source silicon for semiconductors, because you don't have to spend as much money to purify it; also they are used for high-purity glassware for silicon processing (https://www.thequartzcorp.com/ https://www.wired.com/story/book-excerpt-science-of-ultra-pu... https://archive.md/BMFtO).

More broadly, it's difficult to find a rock where silicon isn't a significant component. It is difficult for me to imagine the level of ignorance that could lead someone to claim that an entire country lacked silicon resources. It could be remedied by reading the first paragraph of the introduction to the English Wikipedia article about silicon (https://en.wikipedia.org/wiki/Silicon).

It turns out to be true that rare earths are used for lots of essential electronics, though most components are devoid of them. Essential electronics are silicon semiconductors (silicon, aluminum, copper, boron, arsenic, phosphorus), metals for wires and traces (copper, tin, lead, silver, gold, zinc), FR4 (glass fiber and epoxy), optoelectronic semiconductors (indium, gallium, phosphorus, arsenic), high-speed semiconductors (indium, phosphorus, gallium, arsenic), inductor cores (steel, silicon, barium, manganese, nickel, zinc again, cobalt, strontium), quartz crystals, and capacitor dielectrics. Capacitor dielectrics include plastics, mica, electrolytic anodized coatings, tantalum or niobium pentoxide, and ceramics. Ceramics include the high-capacitance ferroelectrics (lead, zirconium, titanium, sometimes barium) and the high-stability NP0/C0G paraelectrics.

And this is where you finally got something right! It turns the NP0/C0G dielectrics do often contain rare earths: oxides of neodymium and samarium. There are non-rare-earth alternatives made from silica, manganese, titanium, barium, and zirconium (https://patents.google.com/patent/US5599757A/en) or titanium and magnesium (https://exxelia.com/uploads/PDF/ceramic-capacitor-non-magnet...), but the rare-earth compositions are widely adopted. Perhaps they have slightly higher permittivity (permitting smaller capacitors) or lower costs. I don't know.

Regardless, essential electronics can be made without rare earths with only minor compromises, and of course rare earths are everywhere; they could easily be mined in the US again.

[xxpor]

They don't use silica sand to make semiconductors, they use quartzite. Which isn't available near near Toledo. There's plenty of other places in the US, but first you have to actually know the right mineral to look for.

[kragen]

You say, "They don't use silica sand to make semiconductors, they use quartzite." Even if this were true, quartzite is just silica sand that has been sintered together (naturally, underground). Moreover, Vince Beiser's Wired article (linked above) claims that in fact both high-purity silica sand and lump quartz (probably, as you say, quartzite) are used as sources of silicon.