What are some examples of substances that contain crystalline silica?

Constituting 12% of the Earth's crust, quartz, the most common of the nine crystalline silica polymorphs, is the second most abundant mineral in nature. Practically all mining and quarrying activities involve crystalline silica. Indeed, it is present in all naturally occurring materials that are mined from the ground: sand, gravel, dimension stones, metallic and non metallic mineral ores.