Blue zircon from Ratanakiri, Cambodia

Autor(en)

Manuela Zeug, Lutz Nasdala, Bhuwadol Wanthanachaisaeng, Walter A. Balmer, Fernando Corfu, Manfred Wildner

Abstrakt

Zircon from Ratanakiri Province, north-eastern Cambodia, is well known in the gem trade for its vivid blue colour that results from heat treatment. The untreated brown material turns blue under reducing conditions at ~900-1,000°C. Ratanakiri zircon is characterised by remarkably low contents of trace elements. In particular, the actinides have low concentrations (e.g. approximately 120 ppm U and 95 ppm Th). Together with the very young age of the zircon ( < 1 million years [Ma]), this results in an extremely low self-irradiation dose, which in turn is in agreement with its non-radiation-damaged, nearly perfectly crystalline state. The heat treatment, therefore, does not result in detectable changes in the zircon's structural state. The cause of the blue colour, presumably related to a valence change upon heating in the reducing environment, is still under debate. The absorption of the treated Ratanakiri zircon is decidedly different from that of blue U

⁴⁺-doped and blue V

⁴⁺-doped synthetic ZrSiO

₄. Absorption spectra show a strongly pleochroic band at 18,200- 13,000 cm

^-1 (corresponding to ~550-770 nm wavelength) that is clearly responsible for the treated blue colour; however, its assignment remains unresolved.

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Burapha University, University of Oslo, Chulalongkorn University

Journal

The Journal of Gemmology

Band

36

Seiten

112-132

Anzahl der Seiten

21

ISSN

1355-4565

DOI

https://doi.org/10.15506/JoG.2018.36.2.112

Publikationsdatum

06-2018

Peer-reviewed

Ja

ÖFOS 2012

104026 Spektroskopie, 105116 Mineralogie

Schlagwörter

ASJC Scopus Sachgebiete

Geochemistry and Petrology

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/865ec945-f621-4c7b-b993-1e8db95c89b9