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 
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
High purity quartz has been identified as a strategic resource so a number of countries have started exploring sites or subsiding this sort of quartz mining - Russia, China, Australia and a few others