Smoky Quartz

Smoky quartz is a brown to gray, translucent to transparent variety of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque. The darker, nearly black variety is known as 'Morion'. It is prized for its earthy tones and is the national gemstone of Scotland, where it is known as 'Cairngorm'.

Formation & Geology

The smoky color is not caused by impurities, but by trace amounts of aluminum in the crystal lattice combined with natural radiation from surrounding rocks. When the quartz is exposed to gamma rays over millions of years, the radiation interacts with the aluminum, creating 'color centers' that absorb light. This process is often duplicated in laboratories to create very dark smoky quartz from clear quartz.

Physical Characteristics

Like all quartz, it has a hardness of 7 and a conchoidal fracture. It is often found in large, well-formed crystals in pegmatites and metamorphic rocks. It has a vitreous luster and no cleavage. While it can look very dark in mass, thin slices reveal its translucent, 'smoky' nature. It is extremely durable and stable, resistant to most chemicals except hydrofluoric acid.

Historical Significance

In ancient China, flat panes of smoky quartz were used as the world's first sunglasses to shield the eyes of judges from showing emotion in court. In Scotland, it has been used to decorate Highland dress and kilt pins (Sgian-dubhs) for centuries. It remains a popular 'moody' gemstone in modern jewelry, often used in large statement pieces due to the availability of large, clean crystals.