"Faden quartz" is the anglicized version of the German "Fadenquarz", from the German for thread. It refers to a white center line (sucre) that runs through the crystal. Faden quartz usually occurs in Alpine-type fissures. The line is made up of tiny air bubbles, which result from the crystal breaking and reforming as the fissure expanded. This is a very fine faden quartz specimen; if you do not have one, it is a nice size for many collections.