There are provided method for detecting inclusions in a gemstone comprising illuminating the gemstone by successively producing illumination patterns on the gemstone each selected so as to simultaneously provide an internal uniform illumination of one or more predetermined light exit regions of the gemstone, and each being defined by a unique combination of spaced apart light entrance areas illuminated simultaneously from corresponding illumination directions. The method further comprises capturing a plurality of images of the gemstone when illuminated as indicated above, processing the images and identifying inclusions in the images based on non-uniformities in the internal illumination detected in the images. The illumination patterns can be produced by an illumination system configured to selectively illuminate the spaced apart light entrance areas of the gemstone from corresponding illumination directions. The illumination system can be controlled by a controller configured to cause the system to successively produce the illumination patterns. The images of the gemstone can be captured by an image acquisition device and processed by an image processing system configured for identifying inclusions based on non-uniformities in the internal illumination detected in the images.