Mechanism of thermal conversion of colour and colour centres by heat treatment of amethyst

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Authors:Neumann, E.; Schmetzer, Karl
Author Affiliations:Primary:
Univ. Heidelberg, Mineral. Petrogr. Inst., Heidelberg, Federal Republic of Germany
Volume Title:Neues Jahrbuch für Mineralogie. Monatshefte
Source:Neues Jahrbuch für Mineralogie. Monatshefte, 1984(6), p.272-282. Publisher: E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Federal Republic of Germany. ISSN: 0028-3649
Publication Date:1984
Note:In English. 22 refs.
Summary:The absorption spectra of heat-treated amethysts consist of two absorption bands, the absorption band of green prasiolite at 13,800 cm-1 and the absorption band of yellow or brown quartz centered in the ultraviolet region. In general, both absorption bands which are assigned to FeU+002B;(I6) color centers and to iron-containing particles, presumably Fe2O3, were found to increase in one sample parallel or subsequent to a decrease of the violet amethyst absorption band at 18,350 cm-1. However, the relative intensities of the band of green prasiolite, caused by Fe2+ (I6), and the band of yellow-brown quartz, caused by iron-containing particles, are strongly variable. Thus, the thermal conversion of color in amethyst by heat treatment is mainly dependent on the relative intensities of both absorption bands. Modified journal abstract. [E.v.P.]
Subjects:Amethyst; Color centers; Crystal structure; Experimental studies; Framework silicates; Mineralogy; Minerals; Optical properties; Properties; Quartz; Silica minerals; Silicates; Prasiolite; Thermal conversion
Abstract Numbers:85M/1136
Record ID:1985013445
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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