which are hidden within other rocks, like flint. Chemically, quartz is nearly pure silicon dioxide (SiO 2). When there are no impurities, pure quartz is water-clear and often referred to as ...

Large crystals found in geodes and other rocks are relatively rare. Pink ChalcedonyA pink chalcedony shows off its beauty. Chalcedonies include many types of cryptocrystalline quartz gems and ...