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Growth and post-growth defects in a diamond from Finsch Mine (South Africa)

Giovanna Agrosi, Gioacchino Tempesta, Eugenio Scandale and Jeff W. Harris
Growth and post-growth defects in a diamond from Finsch Mine (South Africa) (in European mineralogical conference 2012, Gerhard Brey (prefacer) and Heidi Hoefer (prefacer))
European Journal of Mineralogy (December 2013) 25 (4): 551-559

Abstract

A diamond from the Finsch mine (South Africa) was investigated by X-ray diffraction topography to characterize the extended defects and to reconstruct the growth history. The sample was a doubly polished triangular diamond slice with a rounded side in which re-entrant corners could be seen and the specimen exhibited anomalous birefringence. X-ray topographs show that the sample is actually a mosaic crystal that developed through aggregation of sub-individual parts during growth: some slightly rotated relative to one another and others twinned. The twin law is by reticular merohedry and consists of the well-known 2-fold rotation around [111]. Micro-Raman spectroscopy data revealed that the main inclusions are pyrope and enstatite trapped in the inner part of the individual. No dislocations nucleated from the silicate inclusions. Growth-sector boundaries, dislocations, grain boundaries and twinning indicate that these features formed during the growth of diamond. Throughout the whole sample and chiefly in the regions showing a lower density of inclusions, packed lamination lines parallel to an octahedral face can be observed. These laminations represent a polysynthetic twinning commonly observed in diamonds which have undergone plastic deformation and are considered to be a post-growth defect. The analysis of the structural defects allows a reconstruction of a complex growth history, characterized by a sequence of alternating episodes of growth and dissolution and, lastly, plastic deformation. This study represents a methodological contribution to the studies on the origin of diamond.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 25
Serial Issue: 4
Title: Growth and post-growth defects in a diamond from Finsch Mine (South Africa)
Title: European mineralogical conference 2012
Author(s): Agrosi, GiovannaTempesta, GioacchinoScandale, EugenioHarris, Jeff W.
Author(s): Brey, Gerhardprefacer
Author(s): Hoefer, Heidiprefacer
Affiliation: Universita degli Studi "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari, Italy
Pages: 551-559
Published: 201312
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
Meeting name: European mineralogical conference 2012
Meeting location: Frankfurt, DEU, Germany
Meeting date: 20120902Sept. 2-6, 2012
References: 38
Accession Number: 2014-002391
Categories: Mineralogy of non-silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
S28°22'56" - S28°22'56", E23°26'46" - E23°26'46"
Secondary Affiliation: University of Glasgow, GBR, United Kingdom
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201403
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