Abstract

Staurolite exhibits a complex IR absorption band system in the range of 3750 to 3250 cm (super -1) due to OH stretching vibrations. The bands show a strong pleochroism with nearly no absorbance in spectra with E//b and strong (intermediate) absorbance in spectra with E//a (E//c). The total integrated absorbance was determined from spectra of (010) staurolite plates. These spectra were polarized with E//a and E//c. The total integrated molar absorption coefficient (epsilon (sub i.tot) = 83000+ or -5000 l.mol H 2 O-1.cm (super -2) ) was calculated using H 2 O contents as determined from independent physico-chemical measurements ("Karl-Fischer" titration). Based on Lambert-Beer's law, the content of the component H 2 O in staurolite is obtained with a relative standard deviation of 9% (1sigma ) using this epsilon (sub i.tot) value and by measuring the total integrated absorbance of the whole band system from polarized spectra of a (010) staurolite plate. The quantitative IR data on staurolite are in good agreement with the IR absorption calibrations for water in minerals by Paterson (1982) and Libowitzky & Rossman (1997).

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