PPT Slide
Smoky quartz is generally transparent to translucent quartz that is gray to black in color. The characteristic color of smoky quartz occurs when rock crystal quartz is exposed to natural radiation from radioactive elements or adjacent radioactive rocks over long periods of time. The process by which this occurs is not completely understood but it has been theorized that the color is the result of altered oxidation states of the silica molecules caused by radiation. The granitoid pluton would be the most likely natural source of the radiation.