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Smoky Quartz

This page kindly sponsored by Henry Minot
Formula:
SiO2
Colour:
gray, brown, black
A variety of Quartz

A smoky-gray, brown to black variety of quartz that owes its color to gamma irradiation and the presence of traces of aluminum built into its crystal lattice (Griffiths et al, 1954; O'Brien, 1955). The irradiation causes the aluminum Al(+3) atoms that replace Si(+4) in the lattice in a [AlO4]- group to transfer an electron to a neighboring monovalent cation (often Li+) and form a [AlO4/Metal0]0 color center (O'Brien, 1955).
The name Morion is used for black smoky quartz.

Smoky quartz is dichroic (from darker yellow-brown to lighter red-brown) when viewed in polarized light. The photo to the left shows the change of color in a smoky quartz crystal that is rotated in front of a LCD display that serves as a source of polarized light.
The color of smoky quartz is sensitive to heat and will pale at temperatures above 200-300°C or by prolonged exposure to UV light. This loss of color can be reverted by gamma irradiation of the crystals.

Smoky quartz can be found in many different environments, but is most characteristic for pockets in igneous rocks and pegmatites. The quartz grains in granites and related rocks are often smoky.
Smoky quartz shows many different habits and crystallographic forms, but needle-like crystals of smoky color are not known.
Crystals that grew at relatively high-temperatures, in particular macromosaic quartz crystals like those found in pegmatites and alpine-type fissures are often evenly colored, whereas crystals from other environments often show a color zonation in the form of multiple phantoms. In scepters and skeleton quartz the color may be more intense along the edges of the crystal.

Note: Very often black or brown crystals that are colored by inclusions of minerals or organic matter are erroneously called "smoky quartz" or "morion". Typical examples of such misnomers are black quartz crystals embedded in sedimentary rocks, as those found in gypsum, anhydrite and limestone in Italy and Spain. True smoky quartz can be distinguished from crystals that are colored by inclusions by its dichroism.


Visit gemdat.org for gemological information about Smoky Quartz.


Classification of Smoky Quartz

Physical Properties of Smoky Quartz

Vitreous
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
gray, brown, black
Comment:
dichroic: darker yellow-brown to lighter red-brown

Chemical Properties of Smoky Quartz

Formula:
SiO2
All elements listed in formula:

Other Names for Smoky Quartz

Name in Other Languages:
Danish:Morion
Estonian:Moorion
Italian:Morione
Latvian:Morions
Lithuanian:Morionas
Norwegian (Bokmål):Røykkvarts
Polish:Morion
Portuguese:Quartzo morion
Russian:Морион
Slovak:Morión
Spanish:Morion
Swedish:Rökkvarts

Other Information

Health Risks:
Quartz is usually quite harmless unless broken or powdered. Broken crystals and masses may have razor-sharp edges that can easily cut skin and flesh. Handle with care. Do not grind dry since long-term exposure to finely ground powder may lead to silicosis.

References for Smoky Quartz

Reference List:
Griffiths, J.H.E., Owen, J., Ward, I.M. (1954) Paramagnetic resonance in neutron-irradiated diamond and smoky quartz. Nature: 173: 439-442.

O'Brien, M.C.M. (1955) The structure of the colour centres in smoky quartz. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences: 231: 404-414.

Marshall, Royal R. (1955) Absorption spectra of smoky quartz from an Arkansas vein deposit and from a Sierran miarolitic granite. American Mineralogist: 40: 535-537.

Chudoba, K.F. (1962) Some relations between the causes of amethyst, smoky quartz, and citrine colors as given by modern science. Mineralogicheskii Sbornik (Lvov): 16: 91-105.

Cohen, A.J., Makar, L.N. (1982) Models for color centers in smoky quartz. Physica Status Solidi (A): 73: 593-596.

Partlow, D.P., Cohen, A.J. (1986) Optical studies of biaxial Al-related color centers in smoky quartz. American Mineralogist: 71: 589-598.

Cohen, A.J. (1989) New data on the cause of smoky and amethystine color in quartz. Mineralogical Record: 20: 365-367.

Internet Links for Smoky Quartz

mindat.org URL:
http://www.mindat.org/min-3689.html
Please feel free to link to this page.
Specimens:
The following Smoky Quartz specimens are currently listed for sale on minfind.com.

Localities for Smoky Quartz

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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