The Structure of Powdered Quartz

Moore, Guy S M; Rose, H. E.

doi:10.1038/242187a0

Cited by 30 publications

(9 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Quartz is one of the most common crustal minerals, and it has been suggested that the transition may also modify the mechanical strength of quartz-rich rocks in the deep crust. Xu et al [2007] and Nikitin et al [2007Nikitin et al [ , 2009 identify weakening and seismic velocity reductions in areas of Tibet which influence the dynamic tectonics of the region. A high abundance of quartz-rich rocks in the lower crust has been proposed as a major triggering factor for initiating deformation, but the role of the phase transition on increasing the potential importance of quartz in controlling such deformation has not been directly investigated.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties of quartz at the α‐β phase transition: Implications for tectonic and seismic anomalies

Peng

Redfern

2013

Geochem Geophys Geosyst

View full text Add to dashboard Cite

[1] The anelastic response of single-crystal and polycrystalline quartz and quartz-rich sandstones to applied stress at low frequencies has been investigated by dynamic mechanical analysis and force torsion pendulum measurements. The dynamic modulus was measured on heating and cooling through the a-b phase transition under shear and bending stress applied at low frequency (~1 Hz). Single crystal quartz shows highly anisotropic properties in both the real and imaginary part of the modulus. Polycrystalline novaculite quartz displays the a-b phase transition temperatures (T c ) around 8 C higher than seen in single crystal quartz, due to the pinning stress effect of grain boundaries. The properties of the sandstone vary with heating and cooling cycles as the cementation and microfracturing of the grain structure changes at high temperature. The phase transition in quartz is ferrobielastic, and as such energy differences between domains in the transformation microstructure arise under conditions of applied shear stress. Pre-transition softening and an increase in anelastic loss above T c are attributed to ferrobielastic switching of incipient domain microstructures that arise in the silica microstructure. The influence of temperature on this microstructure is to induce increased switching of domains as a response to thermal stress inherent in the anisotropic thermal expansion of the polycrystalline structure. These results indicate that ferrobielastic switching in quartz is an important mechanism in controlling changes in mechanical properties. As such, we anticipate that it will induce measurable anomalies in seismic signatures of quartz-rich portions of the Earth's crust in regions of high thermal flux. The transition may also be responsible for observed seismic velocity reductions and tectonic weakening in western North America and in certain parts of Tibetan plateau.

show abstract

Section: Introductionmentioning

confidence: 99%

Mechanical properties of quartz at the α‐β phase transition: Implications for tectonic and seismic anomalies

Peng

Redfern

2013

Geochem Geophys Geosyst

View full text Add to dashboard Cite

show abstract

“…The percussive grinding of quartz (or of other accesory minerals) affects the mineral's particle size, thermal diffusivity, density and reactivity. Moore and Rose [13] observed that if quartz is subjected to prolonged percussive grinding, the inversion-peak size decreased and eventually vanished in the DTA diagram run at 10~ min-\ This was attributed to the formation of amorphous silica (about 25%). The sample was found, however, to have the X-ray structure of crystalline, low quartz (-75%) which changed to high quartz when heated at 573~ In addition, the powdered, ground quartz samples contained about 4% firmly held water (until 800~ sorbed from the atmosphere.…”

Section: Thermal and Grinding Treatments Of Quartzmentioning

confidence: 95%

“…When the DTA of ground quartz was carried out at about 18~ min -1, the 'lost' 573 ~ peak became again quite pronounced, possibly because the dispersion of the inversion over a small range of temperature becomes less and a greater fluctuation of differential temperature is produced. When DTA is carried out at low rates of heating, each fragment of quartz inverts at its own individual inversion temperature, and more time is available for heat to be conducted to the sample as a whole, giving rise to a smaller inversion peak [13],…”

Section: Thermal and Grinding Treatments Of Quartzmentioning

confidence: 99%

Solid-state transformation mechanisms of associated minerals to aluminosilicates

Mendelovici

1997

Journal of Thermal Analysis

View full text Add to dashboard Cite

Thermochemical and mechanochemieal transformation mechanisms of associated minerals in clay (quartz, calcite, A1 and Fe oxyhydmxides) are comparatively examined. The phase transformation sequence resulting from heating and, on the other hand from dry grinding of each of the associated minerals, depends on the structure and physicochemical properties of the starting materials.Grinding treatments may cause local heating and local pressure effects in some selective metal oxides and in calcite, respectively, accounting for their structural conversions.

show abstract

“…inversion characteristics. A dispersion of the inversion over a range of temperature was suggested [1 ], and therefore when thermal effects were observed outside the range of temperature where the e-/~ inversion normally occurs, these were investigated and are reported here. Although the research was mainly concerned with the effect of grinding on the c~-/~ inversion, the findings reported in the present paper relate chiefly to the additional thermal effects of adsorbed water and contamination which occur during grinding.…”

mentioning

confidence: 97%

“…We reported previously [1,2] that when quartz was ground for several hundreds of hours, the disappearance of the c~-/? inversion peak on DTA was caused not by conversion of the quartz to an amorphous phase of silica, but by the formation of a microcrystalline variety of quartz with modified c~-/?…”

mentioning

confidence: 98%

Thermal effects of contamination, adsorbed water and annealing on the DTA of powdered quartz

Moore

Rose²

1979

Journal of Thermal Analysis

Self Cite

View full text Add to dashboard Cite

During the grinding of quartz, water is adsorbed from the atmosphere, but this water gave no detectable thermal effect on DTA because it was evolved uniformly up to 1000 ~ However, in conjunction with an iron contaminant, the adsorbed water was involved in an oxidation reaction causing noticeable thermal effects for quartz powdered in a vibration mill constructed of steel parts. When powdered so finely that the ~--/3 inversion peak at 573 ~ had disappeared, annealing caused a partial redevelopment of the peak but recrystallization of disrupted quartz was too small an effect to give any detectable exothermic peak on DTA.We reported previously [1, 2] that when quartz was ground for several hundreds of hours, the disappearance of the c~-/? inversion peak on DTA was caused not by conversion of the quartz to an amorphous phase of silica, but by the formation of a microcrystalline variety of quartz with modified c~-/? inversion characteristics. A dispersion of the inversion over a range of temperature was suggested [1 ], and therefore when thermal effects were observed outside the range of temperature where the e-/~ inversion normally occurs, these were investigated and are reported here. Although the research was mainly concerned with the effect of grinding on the c~-/~ inversion, the findings reported in the present paper relate chiefly to the additional thermal effects of adsorbed water and contamination which occur during grinding.Contrasting with the c~-/? inversion which occurs on every heating, the liberation of adsorbed water or the oxidation of contaminants, if taken to completion during the first DTA run on a given sample, will not produce thrmal effects or a second or subsequent DTA test. However the possible release of stored grinding energy involving the recrystallization of disrupted surface layers on the particles of quartz, discussed by Lindstr6m [3], must be considered. Any broadening of the e -/~ inversion should produce effects, if observeable, both on the initial DTA and subsequent DTA tests of a given sample, unless annealing reduces the strains within the particles to give a sharpening of the e-/~ peak [2].The thermal effects described in this paper are often very small but, nevertheless, they are real in the sense of being reproducible, both on repeated DTA tests and, except in the case of the anomalous effects reported, from one milling test to another involving quartz from various sources. The interpretation of such small

show abstract

The Structure of Powdered Quartz

Cited by 30 publications

References 6 publications

Mechanical properties of quartz at the α‐β phase transition: Implications for tectonic and seismic anomalies

Mechanical properties of quartz at the α‐β phase transition: Implications for tectonic and seismic anomalies

Solid-state transformation mechanisms of associated minerals to aluminosilicates

Thermal effects of contamination, adsorbed water and annealing on the DTA of powdered quartz

Contact Info

Product

Resources

About