Measurement of Quantitative Colour Values of Ore Minerals Using a Filter-Photocell Method

Abstract

This study describes and discusses the feasibility of the development of an inexpensive filter- photocell system suitable for quantitative colour measurement of ore minerals under the reflected-light microscope. In this study, reflectance measurements of eight minerals were obtained using broad band coloured filters with spectral transmissions approximating to those theoretically required. Using this method, only three measurements of the intensity of reflectance for each mineral and the standard (SiC) were taken using red, green and blue (RGB) filters. Colour values obtained in this study are compared with IMA/COM reference values and are satisfactory to within ±1%. Also, the obtained colour values revealed that it might be possible to apply this simple, rapid and direct method in studies where low-cost instrumentation is required, especially in the teaching of ore mineral identification and quantitative colour theory. It is worth mentioning that although the results of this study are promising, conventional spectral reflectance measurements (380- 740 nm) will remain the best recommended method for obtaining the most accurate colour values.