gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1966.035.274.07 A New Method for the Absolute Measurement of Reflectivity Bradshaw P. M. D. 1 Phillips R. Smith R. A. 2 Department of Geology, University of Durham

Present address: Applied Geochemistry Section, Department of Geology, Imperial College of Science and Technology, London.

Department of Mathematics, Durham.

 6 1966 35 274 861 866 4 6 1965 Copyright © 1966, The Mineralogical Society 1966 Summary

The theory of a new method for the determination of reflectivity at truly normal incidence is described. A parallel light beam falls on the specimen after passing through a glass cube with semi-silvered diagonal mounted at the centre of an optical goniometer. The various reflected beams are measured by a photomultiplier fixed to the telescope of the goniometer. Experiment has proved the validity of the method and the spectral reflectivity of pyrite in air and in oil has been investigated.