Structural and chemical varieties of dioptase, Cu 6 [Si 6 O 18 ] · 6 H 2 O*

✍ Scribed by Breuer, K.-H.; Eysel, W.

• Book ID: 121269779
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 1988
• Tongue: English
• Weight: 658 KB
• Volume: 184
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.1988.184.1-2.1

✦ Synopsis

The thermal behaviour of dioptase was studied in air, in argon and hydrothermally using X-ray powder diffraction at normal and elevated temperatures, thermal analysis (TGA, DTA), electron microscopy, UV spectrometry and chemical analysis methods. With increasing temperature natural green dioptase transforms into a blue polymorph and then is dehydrated to black Cu6Si6018. The three varieties are called green, blue and black dioptase. Structurally they are closely related. At still higher temperatures decomposition via Cu5Si6017 into CuO + Si02 is observed and finally reduction of the CuO to Cu20. * This paper forms part of the Ph. D. Thesis of Breuer (1984). Preliminary results were reported by Eysel and Breuer (1981) and Breuer, Müller and Eysel (1983).