An arrangement for, and a method of, accurately determining at least one optical property, such as coverage and/or symmetry, of a gemstone, employ an energizable, stationary light source for directing light rays at different orientations to an uncovered table of the gemstone, and an energizable, stationary backlight spaced away from a culet of the gemstone. A controller energizes the light source to generate return light from the gemstone for each light ray, and energizes the backlight to illuminate the gemstone from behind. An imager images the return light as a plurality of frontlit images, and images the backlit gemstone as a backlit image. The controller processes at least one of the images to determine the optical property of the gemstone.