Smoky quartz is a colour variety of crystalline quartz. It ranges from a light yellowish brown to a brown that is so dark that is appears to be black. Less desirable specimens have a grayish-brown colour. When cut as a gem, stones with an orangish brown to a reddish brown colour are preferred and deserves praise. Smoky quartz is an inexpensive gem material because it is abundant, found in many locations, and its brown color is not currently in high demand. It is often found in large crystals of excellent transparency with few inclusions.

The colour of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates color centers around aluminum impurities within the crystalline quartz. Amethyst forms in a similar way from the activation of color centers around iron impurities.Some specimens of rock crystal can be given the colour of smoky quartz by irradiation in a laboratory. The exposure can be controlled to vary the colour of the product. This is not often done in a lab because natural smoky quartz is inexpensive and abundant relative to demand. For the same reason, synthetic smokey quartz is seldom produced. Natural smoky quartz with a very dark colour is sometimes heated to lighten its colour.

Smoky quartz is faceted or cut into beads and cabochons. These gems are often used in rings, pendants, necklaces, earrings, and brooches for people who like the yellowish brown to brown colour. Smoky quartz with a dark brown color is often used in men's rings and cufflinks. During the Victorian Period dark brown stones from the Mourne Mountains of Ireland were often used in mourning jewellery. It is a favourite practice material of people who are learning to facet. It is also frequently used as a carving material.

Its sources are found in Northern Areas, Swat and Dir.