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Structure of framboidal pyrite: a single crystal X-ray diffraction study

Structure of framboidal pyrite: a single crystal X-ray diffraction study
Structure of framboidal pyrite: a single crystal X-ray diffraction study
The crystallographic nature of pyrite framboids, self-assembled multicrystalline pyrite, was investigated by single crystal X-ray diffraction. The results show that even morphologically well-organised framboids are not extreme examples of single crystals but are microcrystalline aggregates. Two dimensional diffraction patterns obtained from well-organised framboids composed of relatively few (~1000) microcrystals, are single-crystal like but detailed analysis shows that they are actually produced by the superimposition of XRD reflections from similarly, but not identically, oriented microcrystals. The number of coherent crystallographic orientations of pyrite crystals estimated from a complete Ewald sphere data set obtained from a larger single framboid, were found to be approximately four to five times fewer than the number of the microcrystals that are actually contained in the framboid. The result shows the presence of multiple single crystal-like domains that are arranged in similar crystallographic orientations. The results show that framboids are not formed by a process in which crystallographic control is a primary factor. Framboid self-assembly is probably caused by the aggregation of a large number of similarly sized and shaped pyrite microcrystals that are nucleated in a limited volume. Self-organisation occurs as these microcrystals adopt a minimum energy configuration.
framboidal pyrite, framboid, microcrystal, single crystal XRD, self-organisation
0935-1221
93-98
Ohfuji, Hiroaki
628bb610-0787-4ac3-8c41-c2c3e6f92b2f
Rickard, David
eb25768c-0d34-4299-8240-0123e518e1bd
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Hursthouse, Michael B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da
Ohfuji, Hiroaki
628bb610-0787-4ac3-8c41-c2c3e6f92b2f
Rickard, David
eb25768c-0d34-4299-8240-0123e518e1bd
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Hursthouse, Michael B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da

Ohfuji, Hiroaki, Rickard, David, Light, Mark E. and Hursthouse, Michael B. (2006) Structure of framboidal pyrite: a single crystal X-ray diffraction study. European Journal of Mineralogy, 18 (1), 93-98. (doi:10.1127/0935-1221/2006/0018-0093).

Record type: Article

Abstract

The crystallographic nature of pyrite framboids, self-assembled multicrystalline pyrite, was investigated by single crystal X-ray diffraction. The results show that even morphologically well-organised framboids are not extreme examples of single crystals but are microcrystalline aggregates. Two dimensional diffraction patterns obtained from well-organised framboids composed of relatively few (~1000) microcrystals, are single-crystal like but detailed analysis shows that they are actually produced by the superimposition of XRD reflections from similarly, but not identically, oriented microcrystals. The number of coherent crystallographic orientations of pyrite crystals estimated from a complete Ewald sphere data set obtained from a larger single framboid, were found to be approximately four to five times fewer than the number of the microcrystals that are actually contained in the framboid. The result shows the presence of multiple single crystal-like domains that are arranged in similar crystallographic orientations. The results show that framboids are not formed by a process in which crystallographic control is a primary factor. Framboid self-assembly is probably caused by the aggregation of a large number of similarly sized and shaped pyrite microcrystals that are nucleated in a limited volume. Self-organisation occurs as these microcrystals adopt a minimum energy configuration.

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Submitted date: 30 October 2004
Published date: 2006
Keywords: framboidal pyrite, framboid, microcrystal, single crystal XRD, self-organisation

Identifiers

Local EPrints ID: 24177
URI: http://eprints.soton.ac.uk/id/eprint/24177
ISSN: 0935-1221
PURE UUID: f9b5d911-3006-431b-ad54-de5912fb4baf
ORCID for Mark E. Light: ORCID iD orcid.org/0000-0002-0585-0843

Catalogue record

Date deposited: 27 Mar 2006
Last modified: 19 Nov 2019 01:53

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