Smoky quartz

Smoky quartz
General
Category	Silicate minerals
Formula; (repeating unit)	SiO2
Strunz classification	04.DA.05
Dana classification	75.01.03.01
Crystal system	α-quartz: trigonal trapezohedral class 3 2; β-quartz: hexagonal 622[1]
Space group	Trigonal 32
Unit cell	a = 4.9133 Å, c = 5.4053 Å; Z=3
Identification
Colour	Brown to grey, opaque
Crystal habit	6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive
Twinning	Common Dauphine law, Brazil law and Japan law
Cleavage	{0110} Indistinct
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	7 – lower in impure varieties (defining mineral)
Lustre	Vitreous – waxy to dull when massive
Streak	White
Diaphaneity	Transparent to nearly opaque
Specific gravity	2.65; variable 2.59–2.63 in impure varieties
Optical properties	Uniaxial (+)
Refractive index	nω = 1.543–1.545 ; nε = 1.552–1.554
Birefringence	+0.009 (B-G interval)
Pleochroism	weak, from red-brown to green-brown
Melting point	1670 °C (β tridymite) 1713 °C (β cristobalite)[1]
Solubility	Insoluble at STP; 1 ppmmass at 400 °C and 500 lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2[1]
Other characteristics	lattice: hexagonal, Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic)
References	[2][3][4][5]

Smoky quartz is a brownish grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystal.[6] 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.

Varieties

Morion is a very dark brown to black opaque variety. Morion is the German, Danish, Spanish and Polish synonym for smoky quartz.[7] The name is from a misreading of mormorion in Pliny the Elder.[8] It has a density of 5.4.

Cairngorm is a variety of smoky quartz found in the Cairngorm Mountains of Scotland. It usually has a smoky yellow-brown colour, though some specimens are greyish-brown. It is used in Scottish jewellery and as a decoration on kilt pins and the handles of sgianan-dubha (anglicised: sgian-dubhs or skean dhu). The largest known cairngorm crystal is a 23.6 kg (52 lb) 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.[9]

Sunglasses, in the form of flat panes of smoky quartz, were used in China in the 12th century.[10]

Gallery

Morion variety
Crystals of metazeunerite perched on a complete smoky quartz crystal
Smoky quartz found in a stream
Smoky quartz, from Wushan Spessartine Mine, Fujian Province, China
A large specimen of sceptred smoky quartz from Nevada.
A two-sided cluster of glassy and lustrous, doubly terminated smoky quartz crystals from recent finds in Namaqualand, South Africa. The longest crystal is 8.1 cm.
This is an example of the so-called alligator quartz.
A 'large' specimen from a new find in Minas Gerais.

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References

Deer, W. A., R. A. Howie and J. Zussman, An Introduction to the Rock Forming Minerals, Logman, 1966, pp. 340–355 ISBN 0-582-44210-9
Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (eds.). "Quartz". Handbook of Mineralogy (PDF). III (Halides, Hydroxides, Oxides). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209724.
Quartz. Mindat.org. Retrieved on 2013-03-07.
Quartz. Webmineral.com. Retrieved on 2013-03-07.
Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20 ed.). ISBN 0-471-80580-7.
"Smoky Quartz: Smoky Quartz mineral information and data".
http://www.mindat.org/min-6270.html Morion on Mindat
New Oxford American Dictionary (2nd ed., 2005), p. 1102.
"The Gemstone Smoky Quartz". minerals.net. Retrieved 14 December 2015.
Joseph Needham, Science & Civilisation in China (Cambridge, England: Cambridge University Press, 1962), volume IV, part 1, page 121. Needham states that dark glasses were worn by Chinese judges to hide their facial expressions during court proceedings.

Holden, Edward (1925). "The Cause of Color in Smoky Quartz and Amethyst" in American Mineralologist, vol. 9, pp. 203–252

External links

Mineral Galleries - smoky quartz

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[Deer-1] Deer, W. A., R. A. Howie and J. Zussman, An Introduction to the Rock Forming Minerals, Logman, 1966, pp. 340–355 ISBN 0-582-44210-9

[Handbook-2] Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (eds.). "Quartz". Handbook of Mineralogy (PDF). III (Halides, Hydroxides, Oxides). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209724.

[Mindat-3] Quartz. Mindat.org. Retrieved on 2013-03-07.

[Webmin-4] Quartz. Webmineral.com. Retrieved on 2013-03-07.

[Klein-5] Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20 ed.). ISBN 0-471-80580-7.

[6] "Smoky Quartz: Smoky Quartz mineral information and data".

[7] ttp://www.mindat.org/min-6270.html Morion on Mindat

[8] New Oxford American Dictionary (2nd ed., 2005), p. 1102.

[9] "The Gemstone Smoky Quartz". minerals.net. Retrieved 14 December 2015.

[10] Joseph Needham, Science & Civilisation in China (Cambridge, England: Cambridge University Press, 1962), volume IV, part 1, page 121. Needham states that dark glasses were worn by Chinese judges to hide their facial expressions during court proceedings.