Quartz and Silica Minerals Picture Gallery
2019-6-2 · Quartz and Silica Minerals Gallery. Andrew Alden is a geologist based in Oakland, California. He works as a research guide for the U.S. Geological Survey. Quartz (crystalline silica or SiO2) is the most common single mineral of the continental crust. It is unusually hard for a white/clear mineral, hardness 7 on the Mohs scale.