Quartz deposits can be found in expedition lands (all lands except the one where your farm is), and can also be created in the Research Facility (a special building available in the market for coins from lvl 10).
Not sure if there are any quartz deposits at the location? Check it in the resource menu in the left corner of the screen.
Not sure if there are any quartz deposits at the location? Check it in the resource menu in the left corner of the screen.