Smoky quartz is a brown to black variety of quartz. Like other quartz gems, it is a silicon dioxide crystal. The smoky colour results from free silicon, formed from the silicon dioxide by natural irradiation.
A very dark brown to black opaque variety is known as morion. Morion is the German, Danish, Spanish and Polish synonym for smoky quartz. The name is from a misreading of mormorion in Pliny the Elder. It has a density of 5.4.
^New Oxford American Dictionary (2nd ed., 2005), p. 1102.
^Joseph Needham, Science & Civilisation in China (Cambridge, England: Cambridge University Press, 1962), volume IV, part 1, page 121. Needham states that dark glasses were worn by Chinese judges to hide their facial expressions during court proceedings.