Couldn't find an answer to this when looking. If true, and I am not doubting you here, but if true then the reporting on this is ridiculously bad.
Sorry didn't see a notification, my internet source below:
China is building up domestic production of ultra-pure quartz, which is currently produced predominantly in North Carolina.
www.technologyreview.com
"[Ultra-pure quartz] is actually one example where there’ve been a lot of joint public-private efforts to develop more ultra-pure quartz capacity in China. They’re investing in domestic production because that’s one sector where North America dominates current production. [Two American companies in North Carolina] produce like 180,000 tons of ultra-pure quartz a year; [Jiangsu Pacific Quartz Products, a Chinese company] is scaling up [its capacity] this year from 5,000 to 20,000 tons; and that’s basically all of the global production."