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GEOREF RECORD

Nanometre scale textures in agate and Beltane opal

Taijing Lu, X. Zhang, Ichiro Sunagawa and G. W. Groves
Nanometre scale textures in agate and Beltane opal
Mineralogical Magazine (March 1995) 59 (1): 103-109

Abstract

We have carried out TEM observations of agates of geode origin and Beltane opals. Optically observable individual fibres in agates are composed of many fine fibres which consist of quartz crystallites of 8 to 100 nm in length stacked together parallel to {1120} or {1100} with c-axes perpendicular to the fibre elongation. The optically observable systematic striations in agate are found to consist of cyclic alternation of layers due to variation in grain size and porosity. Large quartz crystals, protruding into the spaces of geodes, represent the last stage of formation of these bands, and are merely a continuation of the banding sequence. Nanometre scale textures of cristobalite fibres were revealed in Beltane opals. The cristobalite crystallites have the size of 3 to 20 nm in length and are also stacked together. Our TEM results suggest that embryonic particles were formed in their corresponding growth environments and agglutinated to form fibres.


ISSN: 0026-461X
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 59
Serial Issue: 1
Title: Nanometre scale textures in agate and Beltane opal
Affiliation: National University of Singapore, Department of Physics, Singapore, Singapore
Pages: 103-109
Published: 199503
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 14
Accession Number: 1995-049859
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: Yamanashi Institute of Gemology and Jewelry Arts, JPN, JapanUniversity of Oxford, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
Update Code: 199518
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