Distinctive properties of rock-forming blue quartz: inferences from a multi-analytical study of submicron mineral inclusions
Authors: Seifert, W.; Rhede, D.; Thomas, R.; Förster, H.-J.; Lucassen, F.; Dulski, P.; Wirth, R.
Source: Mineralogical Magazine, Volume 75, Number 4, August 2011 , pp. 2519-2534(16)
Publisher: Mineralogical Society
Abstract:The study discusses the mineralogical, geochemical and thermometric properties of rock-forming blue quartz from eight worldwide occurrences. Compared to non-blue quartz, blue quartz contains significant amounts of submicron-sized (1 μm–100 nm) and nanometre-sized (<100 nm) inclusions. Mica, ilmenite and rutile constitute the most abundant submicron-sized inclusions, and are formed probably by syngenetic precipitation in the boundary layer between quartz and melt (entrapment model). Nanometre-sized rutile possibly originated by epigenetic exsolution of Ti from the quartz structure (exsolution model). Rayleigh scattering of light by nano-particulate inclusions best explains the origin of the blue colour. Blue quartz is generally Ti-rich (∼100–300 ppm) and formed at high temperatures (∼700°C–900°C). The large number, and high spatial density, of tiny xenocrystic inclusions of Ti-bearing minerals make calculations of crystallization temperatures using the Ti-in-quartz thermometer unreliable. The geological significance of blue quartz remains obscure.
Document Type: Research Article
Publication date: 2011-08-01