https://www.pbs.org/newshour/nation/rescue-crews-rush-to-north-carolina-mountain-towns-cut-off-by-helene-floodwaters
Quick google search shows that China has its own Quartz mines, so I'm not sure if those are unsuitable for certain semiconductors or if the use of "world" here just means
From the article, seems like it was due to unique geological properties.
It does later say that similarly high purity can be reached with synthetic quartz but that it would take time to scale up that industry.