Previous micro-Raman investigations on a wide range of types of microcrystalline silica samples have evidenced the presence of a new silica polymorph, i.e. moganite, in virtually every sample. In order to test the ubiquity of moganite in such geological materials in Romania, micro-Raman measurements were performed on gem-quality microcrystalline quartz (chalcedony, including agate and jasper) and additionally on quasi-amorphous silica (opal, silicified wood) samples from different occurrences. All the studied materials, including the quasi-amorphous varieties contain moganite in variable amounts (from traces up to local concentrations of 75 wt. %). Establishing correlations between colour and texture of the chemically-“pure” micro-crystalline silica samples and their mineralogical composition - as traced by micro-Raman measurements, requires further research.
Pop, Dana; Constantina, Ciprian; Tătar, Dan; and Kiefer, Wolfgang
Raman spectroscopy on gem-quality microcrystalline and amorphous silica varieties from Romania,
Studia UBB Geologia
Available at: http://scholarcommons.usf.edu/geologia/vol49/iss1/art4