Smoky Quartz is another macrocrystalline variety of Quartz. The color can vary from grey to warm brown, clear and light to an almost "solid" looking brown/black. This transparent brown, black or gray color makes the stone easily recognizable. The coloration is due to the natural radiation occurring in its environment (crystals of quartz can also be irradiated in the lab to create the smoke color, it is not recommended as it can be usually identified). Collectors who prefer natural occurrence should now be wary of this when purchasing.

Crystals can also be smoky in color due to the presence of sodium. Today fine specimens are found in Switzerland, the Himalayas, Mexico and Brazil. In the United States, fine elestials and sceptors are found in Nevada, other sites include California, Arkansas and Colorado. Faceted smoky quartz in jewelry used to be sold as "smoky topaz" (in fact, no such gemstone known as smoky topaz). I don't know if that is still common practice but the traders codex does not allow this anymore.

Smoky Quartz occurs mostly in Quartz veins where it forms inside rock cavities (also known as "vugs"). It is also found in the cores of pregmatites, and as a secondary crystal within geodes. It is not unusual to find small cavities inside a crystal of Smoky Quartz which contain water or carbon dioxide and sometimes both. These cavities are called enhydros.

When movement of the liquid and gas inclusions within a cavity can be seen with our naked eye, they are then called as elestial enhydros. If a substantial number of fluid inclusions occur in abundance, the crystal becomes opaque and is called Milky Quartz. Many crystals of Smoky Quartz will form, one grading into the other on a bed of Milky Quartz. Hematite, Chlorite or Goethite are other common mineral inclusions which can be found in smokey quartz.

Smokey Quartz has also been called "Champagne on Ice" and it is the national gem of Scotland, their national scepter contains a large crystal of Smoky Quartz on top.