We have considered the ATR spectra from RRUFF database and compared with infrared spectra, available from literature. As told by Subramanian and Rodriguez-Saona, 2009, ATR is "one of the most commonly used sampling techniques in recent times". When an IR light beam passes from a medium with a high refractive index into "a medium of low refractive index (sample)", we can observe that "at a particular angle of incidence, almost all the light waves are reflected back. This phenomenon is called total internal reflection. In this condition, some amount of the light energy escapes the crystal and extends a small distance (0.1-5 μm) beyond the surface in the form of waves". These waves are the evanescent waves. "The intensity of the reflected light reduces at this point. This phenomenon is called attenuated total reflectance" (Subramanian & Rodriguez-Saona, 2009). "The partial penetration of the IR light by an evanescent wave allows an absorption spectrum to be recorded" (see for instance, QD-Europe). The penetration depth of the evanescent wave is a function of the angle of incidence at the sample surface interface. "Deeper penetration into a sample is achieved with either a smaller incident angle or a lower refractive index ATR crystal" (QD-Europe). It is stressed that an ATR spectrum is "different to that obtained for the same sample when collected as a transmission spectrum", since measurement methods are different, being differences dictated "by the fundamental way the sample information is being collected". In transmission spectroscopy, the light passes through the sample, "whereas ATR spectroscopy is the interaction of light by passage into the surface of a sample species. Note that neither method can be regarded as giving the "correct" spectrumthey are simply different" (QD-Europe). The web site details the role of wavelength and refractive index on the penetration depth of the light. Also, the differences of intensities, the band shift, and the band asymmetries that we observe when an ATR spectrum is compared to a transmission spectrum, are discussed. For instance, regarding the band distortion, it is told that "sometimes in ATR measurements the absorption bands can become slightly asymmetric compared to the bands seen in transmission measurements" (QD-Europe). The deformation of the band shape is due to "the rapid change of refractive index of the sample across the band". "The refractive index of the sample varies from a low value on the short wavelength side of the band to a high value on the long wavelength side. This causes the effective penetration depth to also rapidly increase toward the long wavelength side and causes the characteristic shape of the bands seen" (D-Europe). Is it possible to compare the IR spectral results? Let us consider the observations made by : "in most cases comparison of standard spectra collected in FIR transmission and FIR ATR mode leads to only a few differences. The most obvious, when comparing transmission with ATR, is the distortion of band shape. The ATR band shape appears asymmetrical in the lower wavenumber region when compared to spectra collected in transmission mode. Also, intensity differences are noticed. However, the biggest difference can be the shift of strong absorbing bands moving to lower wavenumbers in ATR mode" . Usually, "the shifts observed are small, approximately 1-10 cm -1 , but for very strong absorbing compounds the shifts observed can be as big as 30-50 cm -1 " . Then the ATR spectra can be "considerably different from transmission spectra with respect to intensities, band shift and band distortions" ). If we could use both techniques, we could obtain databases, for instance, to "identifying unknown pigment samples" (Kendix considers pigments in the framework of analyses of cultural heritage materials). "Perhaps it would be less time consuming and more convenient to try to correct the ATR spectrum to simulate a transmission spectrum by using a correction algorithm" . Besides advanced ATR correction algorithms, we could "try applying the Kramers-Kronig transformation on the ATR spectra". However, "the transformation of spectra are usually problematic". Kendix proposes an example of transformations with algorithm and KK relations on cinnabar ATR spectrum, concluding that it is better to collect both transmission and ATR spectra "to build a database for comparison with unknown samples using both techniques as means of detection and identification". As we have seen, ATR measurement method is producing intrinsically asymmetric bands, and therefore, for the deconvolution of the spectrum, an asymmetric band shape is required. We have shown that, using the asymmetric q-BWF functions, we can determine the components of ATR spectra, useful for comparison with infrared data available from literature. We have obtained good results for barite, celestine and anhydrite. The anglesite case is trickier and requires further investigations.