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Quartz-beta

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Formula:
SiO2
Specific Gravity:
2.5334 (Calculated)
Crystal System:
Hexagonal
Dimorph of:
A high-temperature (> ~573°C) polymorph of silica with a crystal structure very similar to that of quartz, but with a higher symmetry (beta-quartz: hexagonal, quartz: trigonal; Bragg and Gibbs, 1925; Heaney, 1994). Like quartz, beta-quartz occurs in left- and right-handed crystals.

Unstable at room temperature, it cannot be quenched from high temperatures. All "beta-quartz" or "quartz-beta" or "high quartz" in collections actually represent paramorphs of quartz after beta-quartz. This is why on Mindat there's not a single photo labeled "quartz-beta", they are all labeled quartz.

The phase transition is at about 573°C at ambient pressures. When heated quickly, beta-quartz melts at about 1550°C, otherwise it will turn into beta-cristobalite at around 1050°C. The temperature of the phase transition from quartz to beta-quartz increases with pressure.

07388230014946279434169.jpg
Quartz paramorph after beta-quartz in rhyolite matrix
00850420014946279444645.jpg
Quartz paramorph after beta-quartz grown in a cavity
07388230014946279434169.jpg
Quartz paramorph after beta-quartz in rhyolite matrix
00850420014946279444645.jpg
Quartz paramorph after beta-quartz grown in a cavity
07388230014946279434169.jpg
Quartz paramorph after beta-quartz in rhyolite matrix
00850420014946279444645.jpg
Quartz paramorph after beta-quartz grown in a cavity


"Beta-quartz" is most commonly found in silica-rich volcanic rocks like rhyolite, in which it occurs as stubby, bipyramidal and usually dull and gray crystals/paramorphs embedded in the matrix. This has led people to believe that quartz crystals with a bipyramidal habit from other, non-volcanic localities grew as beta-quartz, and the habit is unfortunately called "beta-type" or similar.

However, "beta-quartz" that grows freely in cavities frequently forms elongated crystals that are very similar to quartz, or even as very thin, needle-like crystals Eg: https://www.mindat.org/photo-214061.html.










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Physical Properties of Quartz-betaHide

Density:
2.5334 g/cm3 (Calculated)

Chemical Properties of Quartz-betaHide

Formula:
SiO2

Crystallography of Quartz-betaHide

Crystal System:
Hexagonal
Class (H-M):
6 2 2 - Trapezohedral
Space Group:
P64 2 2
Cell Parameters:
a = 4.9977 Å, c = 5.4601 Å
Ratio:
a:c = 1 : 1.093
Unit Cell V:
118.11 ų (Calculated from Unit Cell)

Synonyms of Quartz-betaHide

Other Language Names for Quartz-betaHide

German:Hochquarz

Common AssociatesHide

Associated Minerals Based on Photo Data:
5 photos of Quartz-beta associated with CalciteCaCO3
1 photo of Quartz-beta associated with Plume AgateSiO2
1 photo of Quartz-beta associated with Iris AgateSiO2
1 photo of Quartz-beta associated with δ-QuartzSiO2
1 photo of Quartz-beta associated with
1 photo of Quartz-beta associated with AegirineNaFe3+Si2O6
1 photo of Quartz-beta associated with QuartzSiO2

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Quartz-betaHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Drugman, J. (1911) An example of quartz twinned on the primary rhombohedron. Mineralogical Magazine: 16: 112-117.
Bragg, W., Gibbs, R.E. (1925) The structure of α and β quartz. Proceedings of the Royal Society of London, Series A: 109(751) 405-427.
Heaney, P.J. (1994) Structure and chemistry of the low-pressure silica polymorphs. In: Reviews in Mineralogy, Volume 29, Silica - Physical behavior, geochemistry and materials applications. Mineralogical Society of America, Washington, D.C.

Internet Links for Quartz-betaHide

 
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