A method of assessing a fluorescence characteristic of a sample gemstone, comprising: by a computer with a processor and memory, receiving multiple pairs of image data of captured images of a full view of the sample gemstone under both UV illumination and non-UV illumination, wherein each pair of the non-UV images and the UV images are captured under identical conditions except the illumination light source, wherein each pair of non-UV and UV images is captured at uniquely different image rotational angles but a constant image view angle extracting an outline mask from the non-UV image data by removing any background surrounding the sample gemstone in the received image data; extracting an apparent fluorescence area based on the UV image data, comparing the outline mask and the apparent fluorescence area to determine if any part of the apparent fluorescence area falls outside of the outline mask; excluding any apparent fluorescence area that is determined to be outside the outline mask; constructing a plurality of fluorescence masks, one for each of the image pairs based on the outline mask analysis of each of the color image pairs; quantifying individual color components in each pixel in each of the fluorescence masks in each of the fluorescent images of the plurality of fluorescent images, thereby converting values for individual color components to one or more parameters representing the color characteristic of each pixel within each of the plurality of fluorescence masks; determining an average value for each of the one or more color parameters for all pixels in all image pairs; and calculating a first fluorescence score of the sample gemstone based on the average values of the one or more parameters of all pixels in the image pairs. by a computer with a processor and memory, receiving multiple pairs of image data of captured images of a full view of the sample gemstone under both UV illumination and non-UV illumination, wherein each pair of the non-UV images and the UV images are captured under identical conditions except the illumination light source, wherein each pair of non-UV and UV images is captured at uniquely different image rotational angles but a constant image view angle extracting an outline mask from the non-UV image data by removing any background surrounding the sample gemstone in the received image data; extracting an apparent fluorescence area based on the UV image data, comparing the outline mask and the apparent fluorescence area to determine if any part of the apparent fluorescence area falls outside of the outline mask; excluding any apparent fluorescence area that is determined to be outside the outline mask; quantifying individual color components in each pixel in each of the fluorescence masks in each of the fluorescent images of the plurality of fluorescent images, thereby converting values for individual color components to one or more parameters representing the color characteristic of each pixel within each of the plurality of fluorescence masks; determining an average value for each of the one or more color parameters for all pixels in all image pairs; and calculating a first fluorescence score of the sample gemstone based on the average values of the one or more parameters of all pixels in the image pairs. <EOS>