Smoky Quartz

There are not very many black or dark brown gemstones. There is diamond, onyx and schorl tourmaline, and one sometimes comes across dravite tourmalines, scapolites or agates that are dark brown. However, the most common fine gemstone endowed with this rare and very special colour, is Smoky Quartz.

The traditional material used to make the clairvoyant’s crystal ball, Smoky Quartz has a reputation for being good for both the body and the soul, warding off negative energy and restoring physical and spiritual harmony, hence its frequent use in lithotherapy.

Fashion, too, has adopted it, particularly nowadays with warm, earthy colours being very fashionable. Its red, brown and chocolate shades – according to the intensity of each – garner support with those who appreciate its gentle, warm nuances and its somewhat “tribal” look.

Smoky Quartz is divided into several sub-varieties. Cairngorm is the Smoky Quartz that comes from the Cairngorm Mountains in Scotland; it is usually of a smoky brown-yellow colour, although some Cairngorms are grey-brown. The largest known specimen is a 23.6kg crystal kept in BraemarCastle in Scotland. Morion is a very dark brown to opaque black variety, commonly found in the Alps. There are other sub-varieties of Smoky Quartz, such as the “coon tail” quartz, which has areas of black and grey bands or the Gwindel, a formation of Smoky Quartz with almost parallel crystals, each slightly twisted in relation to its neighbour.

The colour of Smoky Quartz is usually more homogenous than that of amethyst, although it is often more intense at the extremities of the crystals. Having said that, crystals that have unequal zones or colours are not uncommon. Smoky Quartz can even contain purple or yellow zones mixed with its smoky shades. These different colours can appear in different layers known as “phantoms”, or be dispersed unequally within the crystal. Smoky Quartz is also dichroic, indicating that it can present a colour spectrum from yellow-brown to red-brown when it is held under a polarised light.

The dark colour of Smoky Quartz can sometimes come as a result of impurities such as organic composites or manganese oxide, in which case the gemstones should not be called “Smoky Quartz”. This name is reserved for quartz where the colour has been induced through irradiation.

Smoky Quartz is associated with the zodiac sign of Capricorn and is the birthstone of people born in January.

Smoky Quartz Origins and Sources

Smoky Quartz is a macrocrystalline silicium dioxide. It is a member of the quartz family along with amethyst, citrine and several other varieties. This kind of quartz comes in the form of large crystals that are visible to the naked eye. Macrocrystalline quartz is generally transparent to translucent with a vitreous lustre.

The colour of Smoky Quartz varies from brown to black, passing through smoky grey. Its characteristic tint is formed when the quartz crystals are exposed to natural radioactivity for long periods. It is due to the irradiation of the aluminium salts traces contained within.

Quartz is usually found in igneous rock and some metamorphic rocks such as granite and orthogneiss which contain the traces of radioactive elements whose radiation is responsible for the colour of quartz.

Smoky Quartz that comes from volcanic rock is rarer; this is predominantly where clear quartz and amethysts abound. Smoky Quartz that comes from sedimentary rocks is extremely unusual. Most “smoky” quartz that is described as coming from sedimentary rock is not in fact Smoky Quartz, but quartz containing black or brown inclusions.

Smoky Quartz takes a very long time to acquire a deep colour, and it can only do so at temperatures below 50°C. The host rock, therefore, has to be lifted to low temperature zones long before quartz crystals can acquire their tint. That is why Smoky Quartz – and particularly Morion - is generally only found in high places, where the rocks cooled two to eight million years earlier than those of the plains and valleys.

Smoky Quartz comes from a number of sources scattered around the globe. Among the most remarkable, we can cite Brazil, the largest supplier in the world; the Pikes Peak region in Colorado (USA), where it is associated with green amazonite; and the Swiss Alps, from which tons of fine specimens have been extracted.

There are also secondary sources in Canada, Madagascar, India and Pakistan.

Smoky Quartz Value and Treatment

Smoky Quartz is one of the most affordable gemstones. Its value depends largely on the quality of the gemstone, the intensity and the uniformity of its colour. Smoky Quartz can be found in several degrees of clarity. Gemstones without inclusions are obviously worth more. Included Smoky Quartz is commonly cut into beads or cabochons. As this gemstone is quite abundant even in larger sizes, its value per carat does not increase with size.

Most Smoky Quartz which is found in gemstone boutiques or at some lapidaries has been artificially treated with irradiation in order to obtain a black or very dark colour. It is fairly common practice to irradiate colourless quartz in order to sell it as Smoky Quartz. As a result of this, at major fairs vendors are obliged to clearly label this kind of quartz, but it is impossible to tell whether the source of irradiation was natural or not merely by examining the crystal, which explains why certain vendors do nothing and get away with it. Many consumer products are irradiated with gamma rays for sterilisation purposes, so it is easy enough to slip a box of white quartz onto a conveyor belt between a couple of crates of tomatoes two or three times. It sometimes happens that vendors push the radiation dose too far and the crystals turn a dubious shade of black. It is advisable to exercise caution when purchasing from unconfirmed sources.