Category Oxide minerals Strunz classification 04.DA.05 Space group Trigonal 32 | Formula
(repeating unit) SiO2 Dana classification 75.01.03.01 | |
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Crystal system α-quartz: trigonal trapezohedral class 3 2; β-quartz: hexagonal 622 | ||
Smoky quartz is a grey, translucent variety of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque. Some can also be black. 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.
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Morion
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.
Cairngorm
Cairngorm is a variety of smoky quartz crystal found in the Cairngorm Mountains of Scotland. It usually has a smokey yellow-brown colour, though some specimens are a grey-brown.
It is used in Scottish jewellery and as a decoration on kilt pins and the handles of sgian dubhs (anglicised: skean dhu). The largest known cairngorm crystal is a 23.6 kg (52 pound) specimen kept at Braemar Castle.
Uses
Smoky quartz is common and was not historically important, but in recent times it has become a popular gemstone, especially for jewellery.
Sunglasses, in the form of flat panes of smoky quartz, were used in China in the 12th century.