Smoky Quartz colors vary from brown to smoky gray to black. The characteristic smoke color of Smoky Quartz occurs when rock crystal quartz is exposed to natural radiation over long periods of time. It is known that exposure of transparent quartz to radiation can alter the oxidation states of impurities in the quartz structure, giving varying bodies of Smokey Quartz their unique colors. Smokey Quartz comes from many sources around the world. A few of the more noteworthy locations include Brazil, the Pikes Peak area of Colorado, USA (where it is associated with green Amazonite), and the Swiss Alps.