Smoky quartz
Smoky quartz | |
---|---|
Smoky quartz
|
|
General | |
Category | Silicate mineral |
Formula (repeating unit) |
SiO2 |
Strunz classification | 04.DA.05 |
Dana classification | 75.01.03.01 |
Crystal symmetry | 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 |
Crystal system | α-quartz: trigonal trapezohedral class 3 2; β-quartz: hexagonal 622[1] |
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 | None |
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 | Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic) |
References | [2][3][4][5] |
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.[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.
Contents
Varieties
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.[7] The name is from a misreading of mormorion in Pliny the Elder.[8] 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 jewelry 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 jewelry.[9]
Sunglasses, in the form of flat panes of smoky quartz, were used in China in the 12th century.[10]
Gallery
See also
References
- ↑ 1.0 1.1 1.2 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
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Quartz. Mindat.org. Retrieved on 2013-03-07.
- ↑ Quartz. Webmineral.com. Retrieved on 2013-03-07.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Smoky Quartz on Mindat
- ↑ http://www.mindat.org/min-6270.html Morion on Mindat
- ↑ New Oxford American Dictionary (2nd ed., 2005), p. 1102.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 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.
Wikisource has original text related to this article: |
- Holden, Edward (1925). "The Cause of Color in Smoky Quartz and Amethyst" in American Mineralologist, vol. 9, pp. 203-252
External links
Wikimedia Commons has media related to Lua error in package.lua at line 80: module 'strict' not found.. |
<templatestyles src="Asbox/styles.css"></templatestyles>