WATER SPECIATION IN QUARTZ - A NEAR-INFRARED STUDY

Water speciation in quartz has been investigated by infrared and near-infrared spectroscopy and by transmission electron microscopy (TEM). Water-related point defects cannot be distinguished from as-grown tiny aggregates of molecular water by infrared spectroscopy, except if water occurs in the form of bubbles large enough for water to be a fluid phase. In very "wet" quartz (a few hundred atomic ppm or more), water molecules in aggregates represent the prominent species. We show that water can also be incorporated in the form of a supersaturated solution of point defects with a concentration as high as 180 atomic ppm in some synthetic samples. In the case of a solution of water point defects, the near infrared absorbance spectra are expected to exhibit a pleochroism, which has been evidenced using polarized light. However, it has not been possible to fully characterize the structure of these water-associated point defects because of the low absorbance in this spectral range.