Approximately 40 different reservoir and surface rock samples were lased using high power COIL (λ = 1.315 μm), CO2 (λ = 10.6 μm) and Nd:YAG (λ = 1.06 μm) lasers. Spectrum of the samples in the wavelength region from 0.35 to 15.387 μm was obtained. The objectives of this research are to make a detailed study of the spectral properties and optic signatures of rock samples, including reservoir rocks collected from a depth of more that 8,000 ft, in order to predict the energy absorbed when a laser hits a rock. The optical coefficients [extinction/reflection (E), scattering (S), absorption (K) and emission (F)] of these rocks are critically investigated against rock chemistry, grain size, mode of occurrence, porosity, cementing matrix and rock textures, and total organic content. This research, initiated for the petroleum industry, develops a relationship between reflectance and rock properties that are commonly known and used as correlation parameters for other reservoir characterization uses. Our results show that: (1) More than 25% of the COIL and Nd:YAG laser energy is reflected and/or scattered by rocks with more than 85% SiO2 content. (2) Surface and reservoir sandstones have almost the same spectral features and hence similar optic coefficients. (3) Rocks with high porosity have greater reflection coefficients (at the COIL and Nd:YAG wavelengths) compared to those having lower porosity. (4) The reflectance at the CO2 laser wavelength (10.6 μm) is not a function of porosity or grain size.