Blue zircon from Ratanakiri, Cambodia
- Author(s)
- Manuela Zeug, Lutz Nasdala, Bhuwadol Wanthanachaisaeng, Walter A. Balmer, Fernando Corfu, Manfred Wildner
- Abstract
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(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Burapha University, University of Oslo, Chulalongkorn University
- Journal
- The Journal of Gemmology
- Volume
- 36
- Pages
- 112-132
- No. of pages
- 21
- ISSN
- 1355-4565
- DOI
- https://doi.org/10.15506/JoG.2018.36.2.112
- Publication date
- 06-2018
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 104026 Spectroscopy, 105116 Mineralogy
- Keywords
- ASJC Scopus subject areas
- Geochemistry and Petrology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/865ec945-f621-4c7b-b993-1e8db95c89b9