The universal healing stone that has been used as a substitute for more expensive gemstones throughout time. 12% of the earth's crust is composed of this 'rock crystal'. Because quartz is harder than glass, it was commonly used to make crystal balls in the middle Ages.
There are two forms of quartz; Macrocrystalline quartz (quartz that is recognizable with the naked eye) and Microcrystalline or Cryptocrystalline quartz (too small a crystal to be seen without high magnification, such as chalcedony). Both kinds are found in Brazil, Madagascar, Namibia, both the French and Swiss Alps and the U.S.