Quartz is strategic raw material in the modern world, it is the main source of silicon for the high technical industries such as solar cells, semiconductors and optical fibers. Therefore, quartz resources became the main target of many geologists and mineralogists. in this book we deal with some quartz deposits of postmagmatic origin in Egypt. the study include detail qualification study (Geology, Mineralogy, Geochemistry, Crystallinity and reactivity) of such deposits for advance and high technical applications.