The quartz display shows the various colors and forms quartz can be found in.  It demonstrates how quartz forms in different colors due to chemical composition.  Clear quartz is formed when silicon and oxygen bond together, however, amethyst another form of quartz that is purple, forms when silicon, oxygen, and iron bond together.  The addition of iron is what makes this quartz appear purple.  The largest display of amethyst at the Gillespie is the 700 pound vug that contains 500,000 carats of the mineral which further illustrates the different forms quartz can be found in.