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    STUDIA GEOLOGIA - Issue no. 1 / 2004  
         
  Article:   RAMAN SPECTROSCOPY ON GEM-QUALITY MICROCRYSTALLINE AND AMORPHOUS SILICA VARIETIES FROM ROMANIA.

Authors:  DANA POP, CIPRIAN CONSTANTINA, DAN TĂTAR, WOLFGANG KIEFER.
 
       
         
  Abstract:  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” microcrystalline silica samples and their mineralogical composition - as traced by micro-Raman measurements, requires further research.  
         
     
         
         
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