An improvement in the processing of bituminous sands is described, whereby the concentration of bitumen in tar sand feed is measured by infrared light reflected from the tar sand surface. Near infrared is shone onto the surface of the incoming tar sand and reflected light is collected and passed through two parallel filters, one being a measuring filter having a wavelength range of 2180 to 2260 nm and the other being a reference filter having a wavelength range of 2270 to 2350 nm. The beams emerging from the filters are measured electronically and the resulting signals are separately integrated and amplified by electronic means. The ratio of the amplified signals is used to provide a read-out signal responsive to the bitumen concentration. The results may be used to adjust processing conditions in the extraction process to allow for the variations of bitumen in the feed.