The rock crystal is a very well-known and popular gemstone, which can be worked into the most different pieces of jewellery. It belongs to the varieties of the mineral quartz. A rock crystal is usually transparent and has a glassy luster. In white and clear execution it should show no inclusions as a high-quality gemstone and should also be only a little clouded. The term rock crystal stands for one of the purest quartz appearances and has a very similar appearance to diamonds. Since rock crystals are after the feldspar group the most common minerals in the world, the price even for high-quality rock crystals is not comparable with the level of diamonds. By the use of rock crystal in a certain way an inexpensive diamond imitate can be created, which also has a high quality. In addition to their use in jewellery, quartz crystals are also used for industrial purposes. As resistant vessels for chemicals, as abrasives or as components of refractory stones. Rock crystals can become very large, copies of this mineral with a length of more than one meter have already been found.