A method for inspection of a sample having a surface layer. The method includes acquiring a first reflectance spectrum of the sample while irradiating the sample with a collimated beam of X-rays, and processing the first reflectance spectrum to measure a diffuse reflection property of the sample. A second reflectance spectrum of the sample is acquired while irradiating the sample with a converging beam of the X-rays. The second reflectance spectrum is analyzed using the diffuse reflection property so as to determine a characteristic of the surface layer of the sample.