Quartz, especially the purest and highest grade of the form, is of paramount importance to the creation of electronics. That has not changed even after the Apocalypse.
Quartz is key in the production of important materials such as Glass and Silicon, as well as a range of Tier IV and V weapons, armor and equipment, such as the Stun Baton.
In Judgment, quartz is a Tier IV scavenged crafting material that can be obtained during combat missions, and used for crafting.
Quartz can only be found in Quarry locations, deep within the savannah biome.