Transformation mechanisms of tridymite to cristobalite studied by transmission electron microscopy

Ashworth, J. R.

doi:10.1007/bf00307513

Cited by 13 publications

(9 citation statements)

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“…Their boundaries are parallel to the layer plane and in strict lattice orientation with respect to the tridymite (Ashworth, 1988). Although all three tridymite polymorphs can be located within a few #m of this cristobalite, only PO was identified in direct contact with the lamellae.…”

Section: Distribution Of Polymorphsmentioning

confidence: 95%

“…The cristobalite produced in these specimens is described by Ashworth (1988). Material for TEM was prepared by ion-beam thinning from doubly-polished thin-sections.…”

Section: Methodsmentioning

confidence: 99%

“…These high-low inversions are displacive (do not involve breaking of bonds), in contrast to the reconstructive (bond-breaking) transformation of tridymite to cristobalite, of which a TEM study has been presented (Ashworth, 1988). Low tridymites have been characterized by X-ray diffraction (XRD).…”

Section: Introductionmentioning

confidence: 99%

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Transmission electron microscopy of coexisting low-tridymite polymorphs

Ashworth¹

1989

Mineral. mag.

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Three polymorphs of tridymite (MC, PO-10 and MX) have been examined by transmission electron microscopy (TEM), in crystals which also contain lamellae of cristobalite. MX is the least common, and is highly unstable in the electron beam. It occurs as small regions (< 1 /~m 2) in PO-10 tridymite and at MC/PO-10 boundaries; these regions are interpreted as being strained. A consistent association between PO-10 and the cristobalite lamellae is attributed to the fact that PO-10 can more closely match the low-cristobalite structure than MC can, at boundaries parallel to the plane in which the crystal structures contain layers of SiO4 tetrahedra. An analogous interpretation explains the observation that twin boundaries (associated with 60 ~ or 120 ~ rotation of the layer) are commonly parallel to the layer plane in PO-10 but at high angles to it in MC. Abundant lamellar features, parallel to the same plane in PO-10, are tentatively interpreted as representing twinning by reflection and 180 ~ rotation, which may also account for c* streaking in diffraction patterns.

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Section: Distribution Of Polymorphsmentioning

confidence: 95%

“…The cristobalite produced in these specimens is described by Ashworth (1988). Material for TEM was prepared by ion-beam thinning from doubly-polished thin-sections.…”

Section: Methodsmentioning

confidence: 99%

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Transmission electron microscopy of coexisting low-tridymite polymorphs

Ashworth¹

1989

Mineral. mag.

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“…The phase association obtained by firing kaolinite at T R 1200 C is orthorhombic mullite (Al 6 Si 2 O 13 ) and cristobalite [4,5,25,43]. Since cristobalite tends to crystallize or to break up through b / a inversion into very small crystals [3,41], this feature could explain the amorphous aspect of the matrix of the crucibles observed under the SEM (Fig. 7), although the XRD spectra do not show a high background due to the occurrence of amorphous phase.…”

Section: Temperature In Service Conditionsmentioning

confidence: 99%

The glass-melting crucibles of Derrière Sairoche (1699–1714 AD, Ct. Bern, Switzerland): a petrological approach

Eramo

2006

Journal of Archaeological Science

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“…Static compression and olivine flotation experiments to 6 GPa and 2000°C have shown that ultrabasic silicate liquids may be denser than their equilibrium coexisting olivine and pyroxene phases at high pressure conditions [ Agee and Walker , 1988]. Within the Griggs' apparatus, precise high‐temperature/high‐pressure creep measurements have been made to 3 GPa [ Borch and Green , 1989; Green and Borch , 1989]. In addition, faulting associated with the olivine‐spinel transformation has been experimentally investigated leading to speculation on the origin of deep focus earthquakes [ Burnley and Green , 1989; Burnley et al ., 1990].…”

Section: Developments In Large Volume Press Techniquesmentioning

confidence: 99%