Quarz isQuartz is the second most common mineral in Earth's crust and an important component of many types of rock. Quartz crystallises mainly in water-bearing granite systems, where the nominally anhydrous quartz incorporates water into the crystal lattice as defects through coupled exchange reactions. Defect-water contents in Variscan granites (0.3 billion years) are an order of magnitude higher than in Proterozoic granites (0.9-1.8 billion years) from Scandinavia. The water content is reflected in recent sediments and post-Variscan sedimentary rocks and shows a SW-NE gradation. Higher OH contents are preserved in the 1.4 billion year old sandstone from Dalarna/Sweden (Stalder 2021).
