Method and apparatus for classifying defect in component having a monocrystalline structure. The method includes: illuminating surface of component containing defect with beam of light from plurality of different spherical directions; each illumination direction, measuring intensity of light reflected by surface and received by detector; determining contrast value between region with higher intensity and a region with lower intensity for each illumination direction; analyzing contrast values by performing tests selected from the following: (a) determining whether region with higher intensity exceeds predetermined width; (b) identifying illumination direction which produces maximum contrast value, and determining whether illumination direction falls outside of predetermined region; (c) identifying peak in contrast values and determining whether peak extends over range of illumination directions which exceeds predetermined threshold; and (d) determining whether contrast values contain plurality of discontinuous peaks; and determining type of defect based on of tests.