Quartz sand is not as rare a resource as gold or oil, so you don't need to look for quartz deposits because there are none. This creates some confusion for some players who do not yet know where to get the required resource.
Answer: just out of the sea! You can sift quartz sand from water on any coast in unlimited quantities. The number of quartz pits is limited only by free space on your beach - you cannot build buildings for quartz mining on the mainland itself.
From quartz you make the first glasses, and then windows - the main building material of the third level of the population. So without quartz, you simply cannot continue the game.
