The photoluminescence (PL) properties of four gypsums from three localities, namely, Inner Mongolia (China), Turkey, and Canada, are investigated at room temperature. Under 365-nm excitation, two types of gypsums from Inner Mongolia exhibit different luminescence colors, namely, yellow and cyan-white, and gypsums from Turkey and Canada exhibit yellow and bluish-white luminescence, respectively. The PL spectra of these gypsums consist of continuous sub-bands distributed in all visible wavelengths, and the excitation spectra of these gypsums consist of continuous sub-bands distributed in a wide range of wavelengths, i.e., 200-500 nm. The features of PL and excitation spectra suggest that the origin of luminescence from these gypsums may be luminescent organic substances included into crystals in the growth process rather than the impurity ions substituted for Ca~(2+).
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